High-temperature-resistant and high-humidity-resistant protective film and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant and high-humidity-resistant protective film and a preparation method thereof, and belongs to the technical field of protective films, and the film sequentially comprises a surface layer film, a middle layer film and a bottom layer film from top to bottom. Each of the surface layer film and the bottom layer film consists of first low-density polyethylene and a first toughening agent; the middle-layer film is prepared from second low-density polyethylene, a second toughening agent, high-density polyethylene, metallocene polyethylene and an additive; the additive is formed by mixing modified aluminum oxide and modified nano silicon dioxide, the modified aluminum oxide is aluminum oxide modified by phytic acid and a silane coupling agent, and the modified nano silicon dioxide is nano silicon dioxide modified by 4-amino-5-(4-fluorophenyl)-2H-1, 2, 4-triazole-3-thioketone and a silane coupling agent. And after passing through a three-layer co-extrusion film blowing machine, melting, cooling and curling to obtain the high-temperature-resistant and high-humidity-resistant protective film. The protective film prepared by the invention has excellent water resistance, high temperature resistance, antibacterial property and the like, and is suitable for a plurality of application scenes.

Description

Technical Field

[0001] The present invention belongs to the technical field of protective films, and particularly relates to a high-temperature and high-humidity resistant protective film and a preparation method thereof. Background Art

[0002] Polyethylene (PE) is a thermoplastic resin polymerized from ethylene. In industrial applications, it also includes copolymers of ethylene and a small amount of α-olefins. This material is odorless and non-toxic, with a waxy feel, excellent low-temperature resistance, and stable chemical properties, capable of resisting the erosion of most acids and bases (but note to avoid contact with oxidizing acids). As a protective film, polyethylene is widely used in various fields such as stainless steel plates, aluminum plates, aluminum alloy profiles, plastic-steel profiles and their doors and windows, aluminum-plastic panels, fluorocarbon plates, mirror panels, sandwich color steel plates, fireproof boards, decorative panels, and organic glass panels, providing effective protection for the surfaces of various products.

[0003] Polyethylene protective films not only have an affordable price but also usually meet the EU ROHS environmental pollution test standard and meet environmental protection requirements. However, their weather resistance is relatively weak and they are not suitable for long-term use in high-temperature environments. Under high-temperature conditions, polyethylene may undergo thermal decomposition, resulting in a decline in physical and mechanical properties. In addition, the water resistance of polyethylene also has certain limitations, being prone to absorbing moisture, which may then cause product deterioration. This phenomenon is mainly attributed to the lack of hydrophilic groups in the polyethylene molecular structure, making the material prone to moisture absorption and deformation during use. Therefore, in high-temperature and high-humidity environments, the performance of polyethylene protective films will be affected, and there is an urgent need to prepare a high-temperature and high-humidity resistant protective film. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-temperature and high-humidity resistant protective film and a preparation method thereof to solve the problem that the performance of polyethylene protective films will be affected in high-temperature and high-humidity environments.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In the first aspect, the present invention provides a high-temperature and high-humidity resistant protective film, which sequentially includes a surface layer film, a middle layer film, and a bottom layer film from top to bottom.

[0007] Further, both the surface layer film and the bottom layer film are composed of a first low-density polyethylene and a first toughening agent; the middle layer film is composed of a second low-density polyethylene, a second toughening agent, a high-density polyethylene, a metallocene polyethylene, and an additive;

[0008] The additive is composed of modified alumina and modified nano-silica. The modified alumina is alumina modified by phytic acid and silane coupling agent, and the modified nano-silica is nano-silica modified by 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione and silane coupling agent.

[0009] Furthermore, the weight ratio of the modified alumina to the modified nano-silica in the additive is 1:1.

[0010] Furthermore, the preparation method of the modified alumina is as follows:

[0011] Add alumina into an ethanol aqueous solution, stir to obtain a mixed solution; add phytic acid and silane coupling agent KH550 into the mixed solution, heat up to 60 - 80 °C and stir for 1 - 2 h, perform suction filtration, washing, centrifugation, and vacuum drying for 20 - 24 h to obtain the modified alumina.

[0012] Among them, the dosage ratio of alumina, ethanol aqueous solution, phytic acid, and silane coupling agent KH550 is 10 g : 100 mL : 4 - 5 mL : 0.4 - 0.6 g; the volume fraction of the ethanol aqueous solution is 70 - 90%.

[0013] Alumina is a compound composed of two elements, aluminum and oxygen, with high melting point, high hardness, good electrical and thermal conductivity, as well as excellent corrosion and heat resistance. These properties enable alumina to remain stable in high-temperature environments and not easily undergo physical and chemical changes. By adding alumina, the high-temperature resistance of the protective film can be improved. However, the surface of the alumina powder contains a large number of hydroxyl groups, making it highly polar. This high polarity results in a weak adhesion between alumina and non-polar organic materials, thus affecting its dispersibility in composite materials. By using a silane coupling agent for surface modification, an organic silicon film can be formed on the surface of alumina. This film can significantly reduce the surface polarity of alumina, thereby improving its compatibility and dispersibility in raw materials, and enhancing the mechanical properties and high-temperature resistance of the protective film prepared with it as the raw material.

[0014] Phytic acid is a polybasic organic acid, and its molecule contains multiple carboxyl groups (-COOH). In an ethanol aqueous solution, phytic acid can ionize carboxylate anions, and these anions can chelate with aluminum ions on the surface of alumina to form a stable chelate. At the same time, the carboxyl groups of phytic acid can also react with the hydroxyl or alkoxy groups in the silane coupling agent molecule, thereby connecting the silane coupling agent molecule to the surface of alumina. This bridging effect further enhances the binding force between alumina and the silane coupling agent, improves the compatibility and dispersibility of alumina in the raw materials, and improves the mechanical properties and high-temperature resistance of the protective film prepared from it; and phytic acid decomposes at high temperatures to generate small molecules such as phosphoric acid or polyphosphoric acid, etc., which can capture flammable free radicals. After phytic acid burns, a circular structure is formed and adheres to the surface of aluminum hydroxide, making it more difficult for flue gas and toxic gases to be released. At the same time, it blocks the dissipation and propagation of heat, enhancing the flame retardant performance of the protective film prepared from it; phytic acid also has antioxidant properties, can capture free radicals and reduce their destructive effect on the protective film, thereby extending the service life of the protective film.

[0015] Furthermore, the preparation method of the modified nano-silica is as follows:

[0016] Disperse nano-silica, silane coupling agent KH560, 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione in an ethanol aqueous solution, stir at 40 - 50 °C, and dry to obtain modified nano-silica.

[0017] Among them, the dosage ratio of nano-silica, silane coupling agent KH560, 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione, and ethanol aqueous solution is 5 g : 0.1 - 0.2 g : 0.1 - 0.2 g : 60 mL; the volume fraction of the ethanol aqueous solution is 70 - 90%.

[0018] The particle size of nano-silica is at the nano level, which enables them to form a dense micro-nano structure on the material surface. This structure can greatly increase the surface roughness and specific surface area of the material, thereby changing the contact mode between water droplets and the material surface and improving the water resistance of the protective film. However, due to their extremely small size, large specific surface area, and high proportion of surface atoms, nano-silica particles have a very high surface energy. This high surface energy makes the nano-particles in an energy-unstable state and tend to aggregate to reduce the surface energy, resulting in poor dispersibility.

[0019] After the hydrolysis of silane coupling agent KH560, the alkoxy groups are converted into silanol groups, and these silanol groups react with the silanol groups on the surface of nano-silica, significantly improving the dispersibility of nano-silica, and further enhancing the mechanical properties and water resistance of the protective film prepared with it as the base material. 4-Amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione contains a triazole ring and has excellent antibacterial properties, thus improving the antibacterial performance of the protective film. Moreover, this substance contains flame-retardant elements such as nitrogen and sulfur, and through the combined action with the phosphorus element in the above-mentioned modified alumina, the flame-retardant performance of the protective film can be further improved. The epoxy group in silane coupling agent KH560 reacts with the amino group in 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione, and nano-silica and 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione are tightly connected together through chemical bonds. Further, the porous structure of nano-silica can capture or fix triazole thione molecules through physical adsorption, effectively reducing their migration or release from the surface of the protective film, thus ensuring that the protective film can maintain excellent antibacterial and flame-retardant properties for a long time.

[0020] In the second aspect, the present invention provides a method for preparing a high-temperature and high-humidity resistant protective film, comprising the following steps:

[0021] (1) Mix 50-60 parts by weight of the first low-density polyethylene and 4-6 parts by weight of the first toughening agent, and then add them into the barrel of a three-layer co-extrusion blown film machine;

[0022] (2) Mix 50-60 parts by weight of the second low-density polyethylene, 4-6 parts by weight of the second toughening agent, 4-6 parts by weight of high-density polyethylene, 4-6 parts by weight of metallocene polyethylene, and 4-6 parts by weight of an additive evenly, and then add them into the barrel of a three-layer co-extrusion blown film machine;

[0023] (3) After passing through the three-layer co-extrusion blown film machine, it is melted, cooled, and coiled to obtain a high-temperature and high-humidity resistant protective film.

[0024] Furthermore, the extrusion temperature of the three-layer co-extrusion blown film machine is 160°C - 180°C, the blow-up ratio is 2.5 - 3, the draw ratio is 4 - 8, and the draw speed is 200 miles.

[0025] The beneficial effects of the present invention:

[0026] 1. In the raw materials for preparing the protective film of the present invention, modified alumina and modified nano-silica are added. After treatment, the modified alumina and modified nano-silica have good dispersibility, increasing the tensile strength, heat resistance, and water resistance of the protective film. At the same time, the antibacterial, anti-aging, and flame-retardant properties of the protective film are also increased, making the functions of the protective film more diverse and expanding the application scenarios of the protective film.

[0027] 2. The present invention strictly controls the dosages of the modified alumina and the modified nano-silica, because experimental data shows that too high or too low dosages of the modified alumina and the modified nano-silica will affect the comprehensive performance of the protective film. Detailed implementation manners

[0028] The following will describe clearly and completely the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] The parameters of the specific chemical substances in each of the examples and the comparative examples, source:

[0030] Both the first toughening agent and the second toughening agent are ExxonMobil 8203, purchased from ExxonMobil Chemical Company Limited;

[0031] Both the first low-density polyethylene and the second low-density polyethylene are of the model Shell 242H, both purchased from CNOOC and Shell Petrochemical Company Limited;

[0032] High-density polyethylene, grade: BE0400, manufacturer: LG Chem, South Korea;

[0033] The grade of the metallocene polyethylene is 1018MF, purchased from ExxonMobil;

[0034] The CAS number of the alumina is 1344-28-1, purchased from Langfang Naco New Materials Technology Co., Ltd.;

[0035] The nano-silica is purchased from Beijing DeKeDaoJin Technology Co., Ltd.

[0036] Preparation Example 1

[0037] This preparation example provides a modified alumina, and the preparation steps are as follows:

[0038] Add 10 g of alumina into 100 mL of an ethanol aqueous solution with a volume fraction of 70%, stir to obtain a mixed solution; add 4 mL of phytic acid and 0.4 g of silane coupling agent KH550 into the mixed solution, raise the temperature to 60 °C and stir for 1 h, filter by suction, wash, centrifuge, and vacuum dry for 20 h to obtain the modified alumina.

[0039] Preparation Example 2

[0040] This preparation example provides a modified alumina, and the preparation steps are as follows:

[0041] Add 10 g of alumina to 100 mL of an ethanol aqueous solution with a volume fraction of 90%, stir to obtain a mixed solution; add 5 mL of phytic acid and 0.6 g of silane coupling agent KH550 to the mixed solution, heat up to 80 °C and stir for 2 h, filter, wash, centrifuge, and vacuum dry for 24 h to obtain modified alumina.

[0042] Control Example 1

[0043] This control example provides a modified alumina, and the preparation steps are as follows:

[0044] Add 10 g of alumina to 100 mL of an ethanol aqueous solution with a volume fraction of 70%, stir to obtain a mixed solution; add 0.4 g of silane coupling agent KH550 to the mixed solution, heat up to 60 °C and stir for 1 h, filter, wash, centrifuge, and vacuum dry for 20 h to obtain modified alumina.

[0045] Control Example 2

[0046] This control example directly uses alumina.

[0047] Preparation Example 3

[0048] This preparation example provides a modified nano-silica, and the preparation steps are as follows:

[0049] Disperse 5 g of nano-silica, 0.1 g of silane coupling agent KH560, and 0.1 g of 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione in 60 mL of an ethanol aqueous solution with a volume fraction of 70%, stir at 40 °C, and dry to obtain modified nano-silica.

[0050] Preparation Example 4

[0051] This preparation example provides a modified nano-silica, and the preparation steps are as follows:

[0052] Disperse 5 g of nano-silica, 0.2 g of silane coupling agent KH560, and 0.2 g of 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione in 60 mL of an ethanol aqueous solution with a volume fraction of 90%, stir at 50 °C, and dry to obtain modified nano-silica.

[0053] Control Example 3

[0054] This control example provides a modified nano-silica, and the preparation steps are as follows:

[0055] Disperse 5 g of nano-silica and 0.1 g of silane coupling agent KH560 in 60 mL of an ethanol aqueous solution with a volume fraction of 70%, stir at 40 °C, and dry to obtain modified nano-silica.

[0056] Control Example 4

[0057] This comparative example directly uses nano-silica.

[0058] Example 1

[0059] This example provides a high-temperature and high-humidity resistant protective film, which sequentially includes a surface layer film, a middle layer film, and a bottom layer film from top to bottom. Both the surface layer film and the bottom layer film are composed of first low-density polyethylene and a first toughening agent; the middle layer film is composed of second low-density polyethylene, a second toughening agent, high-density polyethylene, metallocene polyethylene, and an additive.

[0060] The preparation method of the high-temperature and high-humidity resistant protective film includes the following steps:

[0061] (1) Mix 60 parts of first low-density polyethylene and 6 parts of the first toughening agent by weight ratio and add them to the barrel of a three-layer co-extrusion blown film machine;

[0062] (2) Mix 60 parts of second low-density polyethylene, 6 parts of the second toughening agent, 6 parts of high-density polyethylene, 6 parts of metallocene polyethylene, 2 parts of modified alumina prepared in Preparation Example 1, and 2 parts of modified nano-silica prepared in Preparation Example 3 evenly, and then add them to the barrel of the three-layer co-extrusion blown film machine;

[0063] (3) After passing through the three-layer co-extrusion blown film machine, it is melted, cooled, and coiled to obtain the high-temperature and high-humidity resistant protective film.

[0064] The extrusion temperature of the three-layer co-extrusion blown film machine is 160 °C, the blow-up ratio is 2.5, the draw ratio is 4, and the draw speed is 200 miles.

[0065] Example 2

[0066] The difference between this example and Example 1 is that step (1) is replaced with: Mix 55 parts of first low-density polyethylene and 5 parts of the first toughening agent and add them to the barrel of the three-layer co-extrusion blown film machine; step (2) is replaced with: Mix 55 parts of second low-density polyethylene, 5 parts of the second toughening agent, 5 parts of high-density polyethylene, 5 parts of metallocene polyethylene, 2.5 parts of modified alumina prepared in Preparation Example 2, and 2.5 parts of modified nano-silica prepared in Preparation Example 4 evenly, and then add them to the barrel of the three-layer co-extrusion blown film machine. The remaining raw materials and steps are the same as those in Example 1.

[0067] Example 3

[0068] This example is different from Example 1 in that step (1) is replaced with: Mix 50 parts of the first low-density polyethylene and 4 parts of the first toughening agent and then add them to the barrel of a three-layer coextrusion blown film machine; step (2) is replaced with: Mix 50 parts of the second low-density polyethylene, 4 parts of the second toughening agent, 4 parts of high-density polyethylene, 4 parts of metallocene polyethylene, 3 parts of the modified alumina prepared in Preparation Example 2, and 3 parts of the modified nano-silica prepared in Preparation Example 4 evenly, and then add them to the barrel of the three-layer coextrusion blown film machine. The remaining raw materials and steps are the same as those in Example 1.

[0069] Example 4

[0070] This example is different from Example 1 in that the process parameters of the three-layer coextrusion blown film machine are replaced with: the extrusion temperature is 180 °C, the blow-up ratio is 3, the draw ratio is 8, and the draw speed is 200 miles. The remaining raw materials and steps are the same as those in Example 1.

[0071] Example 5

[0072] This example is different from Example 1 in that the process parameters of the three-layer coextrusion blown film machine are replaced with: the extrusion temperature is 170 °C, the blow-up ratio is 2.8, the draw ratio is 6, and the draw speed is 200 miles. The remaining raw materials and steps are the same as those in Example 1.

[0073] Comparative Example 1

[0074] This comparative example is different from Example 1 in that "2 parts of the modified alumina prepared in Preparation Example 1 and 2 parts of the modified nano-silica prepared in Preparation Example 3" in Example 1 are replaced with "2 parts of the modified alumina prepared in Comparative Example 1 and 2 parts of the modified nano-silica prepared in Comparative Example 3".

[0075] Comparative Example 2

[0076] This comparative example is different from Example 1 in that "2 parts of the modified alumina prepared in Preparation Example 1 and 2 parts of the modified nano-silica prepared in Preparation Example 3" in Example 1 are replaced with "2 parts of the alumina prepared in Comparative Example 2 and 2 parts of the nano-silica prepared in Comparative Example 4".

[0077] Comparative Example 3

[0078] This comparative example is different from Example 1 in that "2 parts of the modified alumina prepared in Preparation Example 1 and 2 parts of the modified nano-silica prepared in Preparation Example 3" in Example 1 are replaced with "1.5 parts of the modified alumina prepared in Preparation Example 1 and 1.5 parts of the modified nano-silica prepared in Preparation Example 3", and the remaining raw materials and steps are the same as those in Example 1.

[0079] Comparative Example 4

[0080] In this comparative example, compared with Example 3, the difference lies in that "3 parts of the modified alumina prepared in Preparation Example 2 and 3 parts of the modified nano-silica prepared in Preparation Example 4" in Example 3 are replaced with "3.5 parts of the modified alumina prepared in Preparation Example 2 and 3.5 parts of the modified nano-silica prepared in Preparation Example 4", and the remaining raw materials and steps are the same as those in Example 3.

[0081] Perform performance tests on the protective films prepared in Examples 1 - 5 and Comparative Examples 1 - 4. The test items are as follows, and the test results are shown in Table 1:

[0082] I. Tensile strength: Follow the test method of ASTM D - 638 standard.

[0083] II. Heat distortion temperature: ASTM D648 test method: Place a load of 455 kPa or 1820 kPa at the center of the standard test piece, and heat it at a rate of 2 °C / min until the temperature when the deformation is 0.25 mm.

[0084] III. Flame retardancy test: The oxygen index LOI value is tested according to the standard of GB / T 2406.2 - 2009.

[0085] IV. Antibacterial performance test: After cleaning and drying the protective film, cut it into a membrane with a radius of 30 mm and sterilize it under ultraviolet light. After activating Escherichia coli on the plate agar medium for 24 h, take 2 loops and add them to the culture solution, and dilute to a bacterial suspension with a concentration of 1.0×10 CFU / mL. Pipette 0.2 mL of the bacterial suspension and drop it on the protective film, cover the sterilized polyethylene film on the sample, culture it in an incubator at 37 °C for 24 h, wash the sample with the eluent, fully shake and mix the eluted bacteria, inoculate them in the nutrient agar medium, culture them at 37 °C for 24 h, and then perform viable count. The antibacterial rate A = (B - C) / B × 100%; B is the average number of recovered bacteria in the control group; C is the average number of recovered bacteria in the experimental group.

[0086] V. Aging resistance test: 1000 h of light aging (6000 lux), and calculate the tensile strength retention rate.

[0087] VI. Hydrophobicity test: Use a JC2000D2G type contact angle tester to test the water contact angle of the sample.

[0088] Table 1

[0089]

[0090] As can be seen from Table 1, the tensile strength of the protective film prepared by the present invention is above 47.1 MPa, the heat distortion temperature is above 193 °C, the oxygen index is above 42.1%, the antibacterial rate is above 99.81%, the tensile strength retention rate is above 99.87%, and the contact angle is above 122°, showing excellent comprehensive performance.

[0091] In Comparative Example 1, the modified alumina and modified nano-silica were only simply treated with a silane coupling agent, and the properties such as antibacterial and flame retardant properties were reduced, indicating that phytic acid and 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione can improve the flame retardant, antibacterial and aging resistance properties of the protective film.

[0092] In Comparative Example 2, alumina and nano-silica were directly used, and the dispersibility of alumina and nano-silica was poor, resulting in poor comprehensive performance.

[0093] In Comparative Example 3, the addition amount of the modified alumina and modified nano-silica was too small, and in Comparative Example 4, the addition amount of the modified alumina and modified nano-silica was too large, and the comprehensive performance decreased compared with Example 1 and Example 3.

[0094] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0095] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-temperature and high-humidity resistant protective film, characterized in that, The film includes a surface layer film, a middle layer film, and a bottom layer film from top to bottom; both the surface layer film and the bottom layer film are composed of a first low-density polyethylene and a first toughening agent; the middle layer film is composed of a second low-density polyethylene, a second toughening agent, a high-density polyethylene, a metallocene polyethylene, and an additive; The additive is a mixture of modified alumina and modified nano-silica. The modified alumina is alumina modified by phytic acid and a silane coupling agent, and the modified nano-silica is nano-silica modified by 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione and a silane coupling agent.

2. The high-temperature and high-humidity resistant protective film according to claim 1, characterized in that, The weight ratio of modified alumina to modified nano-silica in the additive is 1:

1.

3. The high-temperature and high-humidity resistant protective film according to claim 1, wherein The preparation method of the modified alumina is as follows: Add alumina into an ethanol aqueous solution, stir to obtain a mixed solution; add phytic acid and the silane coupling agent KH550 into the mixed solution, heat up to 60 - 80 °C and stir for 1 - 2 h, perform suction filtration, washing, centrifugation, and vacuum drying for 20 - 24 h to obtain the modified alumina.

4. The high temperature and high humidity resistant protective film according to claim 3, characterized in that The dosage ratio of alumina, ethanol aqueous solution, phytic acid, and silane coupling agent KH550 is 10 g:100 mL:4 - 5 mL:0.4 - 0.6 g.

5. A high temperature and high humidity resistant protective film according to claim 3, characterized in that, The volume fraction of the ethanol aqueous solution is 70 - 90%.

6. The high-temperature and high-humidity resistant protective film according to claim 1, wherein The preparation method of the modified nano-silica is as follows: Disperse nano-silica, silane coupling agent KH560, and 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione in an ethanol aqueous solution with a volume fraction of 70%, stir at 40 - 50 °C, and dry to obtain the modified nano-silica.

7. The high-temperature and high-humidity resistant protective film according to claim 6, characterized in that, The dosage ratio of nano-silica, silane coupling agent KH560, 4-amino-5-(4-fluorophenyl)-2H-1,2,4-triazole-3-thione, and ethanol aqueous solution is 5 g:0.1 - 0.2 g:0.1 - 0.2 g:60 mL.

8. The high-temperature and high-humidity resistant protective film according to claim 6, wherein The volume fraction of the ethanol aqueous solution is 70 - 90%.

9. The preparation method of a high-temperature and high-humidity resistant protective film according to any one of claims 1-8, characterized in that, It includes the following steps: (1) Mix 50 - 60 parts by weight of the first low-density polyethylene and 4 - 6 parts by weight of the first toughening agent and add them into the barrel of a three-layer co-extrusion blown film machine; (2) Mix 50 - 60 parts by weight of the second low-density polyethylene, 4 - 6 parts by weight of the second toughening agent, 4 - 6 parts by weight of the high-density polyethylene, 4 - 6 parts by weight of the metallocene polyethylene, and 4 - 6 parts by weight of the additive evenly and then add them into the barrel of the three-layer co-extrusion blown film machine; (3) After passing through the three-layer co-extrusion blown film machine, it is melted, cooled, and coiled to obtain a high-temperature and high-humidity resistant protective film.

10. The preparation method of a high-temperature and high-humidity resistant protective film according to claim 9, characterized in that, The extrusion temperature of the three-layer co-extrusion blown film machine is 160 °C - 180 °C, the blow-up ratio is 2.5 - 3, the draw ratio is 4 - 8, and the draw speed is 200 mileage.

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