Washable protective film and preparation method thereof

Abstract

The invention discloses a washable protective film and a preparation method thereof, and belongs to the technical field of protective films, the washable protective film comprises the following raw materials by weight: 100 parts of polyethylene glycol terephthalate, 6-8 parts of carbon fiber, 3-8 parts of a modified siloxane polymer, and 0.3-0.6 part of an antioxidant; the modified siloxane polymer is prepared from a flame retardant containing a carbon-carbon double bond, an antibacterial siloxane monomer and 1-dodecene through a polymerization reaction. The washable protective film is prepared by the following steps: weighing polyethylene glycol terephthalate, carbon fibers, a modified siloxane polymer and an antioxidant, uniformly mixing and stirring in a high-speed mixer, melting in a double-screw extruder, and extruding and casting in an extrusion casting machine at the extrusion temperature of 260-280 DEG C to obtain the washable protective film. The obtained protective film is rich in function, good in washing resistance and high in application value.

Description

Technical Field

[0001] The invention belongs to the technical field of protective films, and in particular relates to a water-resistant protective film and a preparation method thereof. Background Art

[0002] There are many types of protective film substrates, including PET (polyethylene terephthalate), PE (polyethylene), PVC (polyvinyl chloride), OPP (oriented polypropylene), PI (polyimide), PEN (polyethylene naphthalate) and PEEK (polyetheretherketone). Among these materials, PET and PE have become the two most commonly used protective film substrates due to their unique advantages. In particular, PET, or polyethylene terephthalate, has won wide application and recognition in many fields such as electronics, packaging, construction, and automobiles due to its significant cost-effectiveness, excellent appearance performance and good recyclability.

[0003] However, despite the many advantages of PET film, its functions are relatively simple and mainly limited to basic protection, which makes it difficult to meet the increasingly diversified and high-end market demands. In addition, PET film still has certain limitations in terms of water washability, especially in application scenarios that need to withstand frequent or high-intensity water washing, its durability and performance stability need to be further improved. Therefore, how to develop a PET protective film with more comprehensive functions and better water washability has become an important issue and challenge facing the current industry. Summary of the invention

[0004] The purpose of the present invention is to provide a water-washable protective film and a preparation method thereof, which solves the problem that the current PET film has a single function and its water-washable performance needs to be improved.

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

[0006] A washable protective film comprises the following raw materials in parts by weight: 100 parts of polyethylene terephthalate, 6-8 parts of carbon fiber, 3-8 parts of modified siloxane polymer, and 0.3-0.6 parts of antioxidant; the modified siloxane polymer is prepared by polymerization of a flame retardant containing a carbon-carbon double bond, an antibacterial siloxane monomer, and 1-dodecene.

[0007] The washable protective film is made by the following steps:

[0008] Weigh polyethylene terephthalate, carbon fiber, modified siloxane polymer and antioxidant, mix and stir evenly in a high-speed mixer, then melt on a twin-screw extruder, and then extrude and cast into a film in an extrusion casting machine at an extrusion temperature of 260-280° C. to obtain a washable protective film.

[0009] Further, the preparation method of the modified siloxane polymer is:

[0010] Step A1: Under an argon environment, DOPO-HQ, undecenoyl chloride, pyrimidine and anhydrous dichloromethane are mixed, stirred at room temperature for 15-20 minutes, and heated to reflux temperature for 15 minutes. After the reaction is completed, the reaction mixture is placed in a separation funnel, washed with water, 2 mol / L hydrochloric acid aqueous solution, and 5 wt% NaHCO3 solution, and dried over anhydrous magnesium sulfate to obtain a flame retardant containing carbon-carbon double bonds;

[0011] The usage ratio of DOPO-HQ, undecenoyl chloride, pyrimidine and anhydrous dichloromethane is 5 g: 6.5 g: 4 mL: 125 mL.

[0012] The hydroxyl group of DOPO-HQ can undergo esterification reaction with the acyl chloride group of undecylenic chloride to generate an ester group, thereby obtaining a flame retardant containing a carbon-carbon double bond.

[0013] Step A2: 4-bromo-1-butene, anhydrous toluene and chloroplatinic acid solution were added to a three-necked flask, triethoxysilane was weighed and placed in a constant pressure funnel, nitrogen was introduced, preheated at 60°C for 60 min, triethoxysilane was added dropwise at 95°C, and refluxed for 8 h. After the reaction was completed, the reaction product was washed with water, allowed to stand for separation, dried over anhydrous calcium chloride, filtered, and toluene was removed by rotary evaporation to obtain bromobutyltriethoxysilane;

[0014] Among them, the usage ratio of 4-bromo-1-butene, anhydrous toluene, chloroplatinic acid solution and triethoxysilane is 6.5g:18g:100μL:9g; the usage ratio of chloroplatinic acid and isopropanol in the chloroplatinic acid solution is 0.25g:25mL.

[0015] Step A3: Dimethylaminoethyl methacrylate, bromobutyltriethoxysilane and acetone are placed in a three-necked flask, nitrogen is introduced, the reaction is carried out at 55° C. for 60 hours, and the acetone is removed by vacuum distillation to obtain a distillate; the remaining distillate is cooled to room temperature, ether is added, cooled to 0° C. for crystallization, and then filtered, washed with anhydrous ether three times, and vacuum dried at 45° C. for 24 hours to obtain an antibacterial siloxane monomer;

[0016] Among them, the mass ratio of dimethylaminoethyl methacrylate, brominated butyltriethoxysilane and acetone is 6:14.5:30.

[0017] After 4-bromo-1-butene and triethoxysilane undergo a hydrosilylation reaction, the quaternization reaction is carried out with dimethylaminoethyl methacrylate to obtain an antibacterial siloxane monomer.

[0018] Step A4: adding a flame retardant containing a carbon-carbon double bond, an antibacterial siloxane monomer, 1-dodecene and water into a four-necked flask, introducing nitrogen gas under stirring, heating to 65° C. after 30 minutes, dripping a 0.3 wt % aqueous solution of azobisisobutylamidine hydrochloride into the four-necked flask in two batches with an interval of 15 minutes, reacting at 65° C. for 8-10 hours to obtain a reaction solution; cooling the reaction solution to room temperature, pouring it into acetone, filtering it with suction, crushing it, soaking and washing it with acetone for 3 times, and vacuum drying it at 60° C. for 24-48 hours to obtain a modified siloxane polymer;

[0019] The dosage ratio of the carbon-carbon double bond-containing flame retardant, the antibacterial siloxane monomer, 1-dodecene, water, and 0.3 wt % azobisisobutyramidine hydrochloride solution is 6.57 g: 0.78 g: 0.08 g: 32 mL: 13 mL.

[0020] The flame retardant containing carbon-carbon double bonds, the antibacterial siloxane monomer and 1-dodecene are polymerized to obtain a modified siloxane polymer.

[0021] Further, the antioxidant is at least one of antioxidant 1010 , antioxidant 2246 , antioxidant 1076 and antioxidant 330 .

[0022] Furthermore, the temperature of each section of the twin-screw extruder is 270-290° C., and the screw speed is 80-100 r / min.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention adds a modified siloxane polymer to the raw materials for preparing the water-resistant protective film. The modified siloxane polymer contains a quaternary ammonium salt group, which has antibacterial properties and can improve the antibacterial properties of the water-resistant protective film. The modified siloxane polymer contains nitrogen, phosphorus, and silicon flame retardant elements. During the combustion process of the water-resistant protective film, the modified siloxane polymer can absorb heat and decompose by heat to form a non-volatile protective layer on the surface of the film and isolate the air, while releasing non-flammable gases such as carbon dioxide, diluting oxygen and flammable cracking gases, and effectively solving the problem of the flammability of the water-resistant protective film. The modified siloxane polymer contains a long hydrophobic chain, which can significantly improve the hydrophobic properties of the water-resistant protective film and achieve a good waterproof effect. The modified siloxane polymer has a low surface tension, which enables them to form a thin lubricating layer between the carbon fiber and the PET matrix. This lubricating layer helps to reduce friction and agglomeration between carbon fibers, making them easier to disperse in the PET matrix, thereby improving the overall strength and toughness of the film; and the low surface energy of the modified siloxane polymer reduces the surface energy of the protective film, weakening the interaction between water molecules and the membrane surface, thereby increasing the tendency of water molecules to detach from the membrane surface, that is, improving the hydrophobicity.

[0025] 2. The present invention strictly controls the ratio of the modified siloxane polymer because experimental data show that too high or too low an amount of the modified siloxane polymer added will affect the performance of the protective film. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] Preparation Example 1

[0028] The preparation method of the modified siloxane polymer in this preparation example is:

[0029] Step A1: Under an argon environment, 5 g of DOPO-HQ, 6.5 g of undecylenic acid chloride, 4 mL of pyrimidine and 125 mL of anhydrous dichloromethane were mixed, stirred at room temperature for 15 min, and heated to reflux temperature for 15 min. After the reaction was completed, the reaction mixture was placed in a separation funnel, washed with water, 2 mol / L hydrochloric acid aqueous solution, and 5 wt% NaHCO3 solution, and dried over anhydrous magnesium sulfate to obtain a flame retardant containing carbon-carbon double bonds;

[0030] Step A2: 6.5 g of 4-bromo-1-butene, 18 g of anhydrous toluene, and 100 μL of chloroplatinic acid solution were added to a three-necked flask, 9 g of triethoxysilane was weighed and placed in a constant pressure funnel, nitrogen was introduced, preheated at 60° C. for 60 min, triethoxysilane was added dropwise at 95° C., and refluxed for 8 h. After the reaction was completed, the reaction product was washed with water, allowed to stand for separation, dried over anhydrous calcium chloride, filtered, and toluene was removed by rotary evaporation to obtain bromobutyltriethoxysilane;

[0031] Step A3: 6 g of dimethylaminoethyl methacrylate, 14.5 g of bromobutyltriethoxysilane and 30 g of acetone were placed in a three-necked flask, nitrogen was introduced, the reaction was carried out at 55° C. for 60 h, and the acetone was removed by reduced pressure distillation to obtain a distillate; the remaining distillate was cooled to room temperature, ether was added, cooled to 0° C. for crystallization, and then filtered, washed with anhydrous ether three times, and vacuum dried at 45° C. for 24 h to obtain an antibacterial siloxane monomer;

[0032] Step A4: 6.57 g of a flame retardant containing a carbon-carbon double bond, 0.78 g of an antibacterial siloxane monomer, 0.08 g of 1-dodecene and 32 mL of water were added to a four-necked flask, nitrogen was introduced under stirring, and the temperature was raised to 65° C. after 30 minutes. 13 mL of a 0.3 wt % aqueous solution of azobisisobutylamidine hydrochloride was dripped into the four-necked flask in two batches at an interval of 15 minutes. After the addition was completed, the reaction was carried out at 65° C. for 8 hours to obtain a reaction solution; the reaction solution was cooled to room temperature and then poured into acetone, filtered, crushed, soaked and washed with acetone for 3 times, and vacuum dried at 60° C. for 24 hours to obtain a modified siloxane polymer.

[0033] Preparation Example 2

[0034] The preparation method of the modified siloxane polymer in this preparation example is:

[0035] Step A1: Under an argon environment, 5 g of DOPO-HQ, 6.5 g of undecylenic acid chloride, 4 mL of pyrimidine and 125 mL of anhydrous dichloromethane were mixed, stirred at room temperature for 20 min, and heated to reflux temperature for 15 min. After the reaction was completed, the reaction mixture was placed in a separation funnel, washed with water, 2 mol / L hydrochloric acid aqueous solution, and 5 wt% NaHCO3 solution, and dried over anhydrous magnesium sulfate to obtain a flame retardant containing carbon-carbon double bonds;

[0036] Step A2: 6.5 g of 4-bromo-1-butene, 18 g of anhydrous toluene, and 100 μL of chloroplatinic acid solution were added to a three-necked flask, 9 g of triethoxysilane was weighed and placed in a constant pressure funnel, nitrogen was introduced, preheated at 60° C. for 60 min, triethoxysilane was added dropwise at 95° C., and refluxed for 8 h. After the reaction was completed, the reaction product was washed with water, allowed to stand for separation, dried over anhydrous calcium chloride, filtered, and toluene was removed by rotary evaporation to obtain bromobutyltriethoxysilane;

[0037] Step A3: 6 g of dimethylaminoethyl methacrylate, 14.5 g of bromobutyltriethoxysilane and 30 g of acetone were placed in a three-necked flask, nitrogen was introduced, the reaction was carried out at 55° C. for 60 h, and the acetone was removed by reduced pressure distillation to obtain a distillate; the remaining distillate was cooled to room temperature, ether was added, cooled to 0° C. for crystallization, and then filtered, washed with anhydrous ether three times, and vacuum dried at 45° C. for 24 h to obtain an antibacterial siloxane monomer;

[0038] Step A4: 6.57 g of a flame retardant containing a carbon-carbon double bond, 0.78 g of an antibacterial siloxane monomer, 0.08 g of 1-dodecene and 32 mL of water were added to a four-necked flask, nitrogen was introduced under stirring, and the temperature was raised to 65° C. after 30 minutes. 13 mL of a 0.3 wt % aqueous solution of azobisisobutylamidine hydrochloride was dripped into the four-necked flask in two batches at an interval of 15 minutes. After the addition was completed, the reaction was carried out at 65° C. for 10 hours to obtain a reaction solution; the reaction solution was cooled to room temperature and then poured into acetone, filtered, crushed, soaked and washed with acetone for 3 times, and vacuum dried at 60° C. for 48 hours to obtain a modified siloxane polymer.

[0039] Preparation Example 3

[0040] In this preparation example, the flame retardant containing carbon-carbon double bonds in step A4 of preparation 1 is removed, and the remaining raw materials and steps are the same as those of preparation example 1.

[0041] Preparation Example 4

[0042] In this preparation example, the antibacterial siloxane monomer in step A4 of preparation 1 is removed, and the remaining raw materials and steps are the same as those of preparation example 1.

[0043] Preparation Example 5

[0044] In this preparation example, 1-dodecene in step A4 of preparation 1 is removed, and the remaining raw materials and steps are the same as those of preparation example 1.

[0045] Example 1

[0046] The washable protective film of this embodiment is made by the following steps:

[0047] Weigh 100 parts of polyethylene terephthalate, 6 parts of carbon fiber, 3 parts of modified siloxane polymer prepared in Preparation Example 1, and 0.3 parts of antioxidant 1076, mix and stir evenly in a high-speed mixer, and then melt them on a twin-screw extruder. The temperatures of each section are 280°C, 270°C, 275°C, 290°C, 275°C, and 285°C, and the screw speed is 80r / min. Then extrude and cast the film in an extrusion casting machine at an extrusion temperature of 260°C to obtain a water-resistant protective film.

[0048] Example 2

[0049] The washable protective film of this embodiment is made by the following steps:

[0050] Weigh 100 parts of polyethylene terephthalate, 7 parts of carbon fiber, 5.5 parts of modified siloxane polymer prepared in Preparation Example 1, and 0.45 parts of antioxidant 2246, mix and stir evenly in a high-speed mixer, and then melt on a twin-screw extruder. The temperatures of each section are 280°C, 270°C, 275°C, 290°C, 275°C, and 285°C, and the screw speed is 90r / min. Then, extrude and cast into a film in an extrusion casting machine at an extrusion temperature of 270°C to obtain a water-resistant protective film.

[0051] Example 3

[0052] The washable protective film of this embodiment is made by the following steps:

[0053] Weigh 100 parts of polyethylene terephthalate, 8 parts of carbon fiber, 8 parts of modified siloxane polymer prepared in Preparation Example 2, and 0.6 parts of antioxidant 1010, mix and stir evenly in a high-speed mixer, and then melt on a twin-screw extruder. The temperatures of each section are 280°C, 270°C, 275°C, 290°C, 275°C, and 285°C, and the screw speed is 100r / min. Then, extrude and cast into a film in an extrusion casting machine at an extrusion temperature of 280°C to obtain a water-resistant protective film.

[0054] Comparative Example 1

[0055] In this comparative example, the modified siloxane polymer prepared in Preparation Example 1 in Example 1 is replaced by the product prepared in Preparation Example 3, and the remaining raw materials and steps are the same as in Example 1.

[0056] Comparative Example 2

[0057] In this comparative example, the modified siloxane polymer prepared in Preparation Example 1 in Example 1 is replaced by the product prepared in Preparation Example 4, and the remaining raw materials and steps are the same as in Example 1.

[0058] Comparative Example 3

[0059] In this comparative example, the modified siloxane polymer prepared in Preparation Example 1 in Example 1 is replaced by the product prepared in Preparation Example 5, and the remaining raw materials and steps are the same as in Example 1.

[0060] Comparative Example 4

[0061] In this comparative example, the modified siloxane polymer prepared in Preparation Example 1 in Example 1 is replaced by polydimethylsiloxane, and the remaining raw materials and steps are the same as in Example 1.

[0062] Comparative Example 5

[0063] The washable protective film of this embodiment is made by the following steps:

[0064] Weigh 100 parts of polyethylene terephthalate, 6 parts of carbon fiber, and 0.3 parts of antioxidant, mix and stir evenly in a high-speed mixer, and then melt them on a twin-screw extruder. The temperatures of each section are 280°C, 270°C, 275°C, 290°C, 275°C, and 285°C, and the screw speed is 80r / min. Then, extrude and cast them into a film in an extrusion casting machine at an extrusion temperature of 260°C to obtain a washable protective film.

[0065] Comparative Example 6

[0066] In this comparative example, "3 parts of the modified siloxane polymer prepared in Preparation Example 1" in Example 1 is replaced by "4 parts of the modified siloxane polymer prepared in Preparation Example 1", and the remaining raw materials and preparation steps are the same as in Example 1.

[0067] Comparative Example 7

[0068] In this comparative example, "8 parts of the modified siloxane polymer prepared in Preparation Example 2" in Example 3 is replaced by "9 parts of the modified siloxane polymer prepared in Preparation Example 2", and the remaining raw materials and preparation steps are the same as in Example 3.

[0069] The water-resistant protective films prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were subjected to performance tests, and the test items were as follows:

[0070] 1. Contact angle test: The hydrophobicity test of the protective film samples prepared in Examples 1 to 3 and Comparative Examples 1 to 7 was performed using a contact angle meter. Specifically, a 0.5 mm needle was used to drop 5 uL of water. Each protective film sample was tested 3 to 5 times and the average value was calculated.

[0071] 2. Waterproof test: Take a cylindrical container with two open ends and a diameter of 5 cm, place the protective film samples prepared in Examples 1 to 3 and Comparative Examples 1 to 7 on one end of the container respectively and cover the lower surface with a piece of filter paper, then put a sealing ring on it and clamp it, with the end with the protective film sample and filter paper facing downward and the open end facing upward, inject water into the container and make the height of the water column 10 cm, observe after 10 hours whether there is water seeping through the sample onto the filter paper, if there is no water seepage, it passes the test, otherwise it fails.

[0072] 3. Antibacterial performance test: After cleaning and drying the protective film, cut it into a film with a radius of 30mm, and sterilize it under ultraviolet light. After the Escherichia coli is inoculated on the flat agar medium and activated for 24 hours, 2 rings are taken and added to the culture medium, and diluted to a bacterial suspension with a concentration of 1.0×10 CFU / mL. Pipette 0.2mL of the bacterial suspension and drop it on the protective film, cover the sterilized polyethylene film on the sample, and culture it in an incubator at 37°C for 24 hours. Wash the sample with the eluent, shake the eluted bacteria thoroughly, inoculate it in the nutrient agar medium, culture it at 37°C for 24 hours, and then count the live bacteria. The antibacterial rate A = (BC) / 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.

[0073] 4. Flame retardant performance test: Oxygen index LO I value is tested according to GB / T 2406.2-2009 standard

[0074] 5. Tensile strength: Tested in accordance with ASTM D638-03 standard.

[0075] The above test results are shown in Table 1.

[0076] Table 1

[0077]

[0078]

[0079] It can be seen from Table 1 that the water-resistant protective film prepared by Examples 1 to 3 has excellent waterproof performance, antibacterial performance, flame retardant performance and tensile strength. Comparative Example 1 does not contain a flame retardant containing carbon-carbon double bonds, lacks the two flame retardant elements of nitrogen and phosphorus, and only has silicon as a flame retardant element, and the overall flame retardant performance is reduced; Comparative Example 2 does not contain antibacterial siloxane monomers, and the overall antibacterial performance and tensile strength are reduced; Comparative Example 3 does not contain 1-dodecene, and the hydrophobic performance of the film is reduced compared with Example 1; in Comparative Example 4, the modified siloxane polymer is replaced with polydimethylsiloxane, and the antibacterial, hydrophobic and flame retardant properties are reduced; Comparative Example 5 is a pure PET film with the worst performance; the amount of modified siloxane polymer added in Comparative Example 6 is too little, and the performance is reduced compared with Example 1; the amount of modified siloxane polymer added in Comparative Example 7 is too much, and the performance is reduced compared with Example 3.

[0080] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0081] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A water-resistant protective film, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polyethylene terephthalate, 6-8 parts of carbon fiber, 3-8 parts of modified siloxane polymer and 0.3-0.6 parts of antioxidant; the modified siloxane polymer is prepared by polymerization reaction of a flame retardant containing carbon-carbon double bonds, an antibacterial siloxane monomer and 1-dodecene.

2. A water-resistant protective film according to claim 1, characterized in that: The preparation method of the modified siloxane polymer is: Step A1: Under an argon environment, DOPO-HQ, undecenoyl chloride, pyrimidine and anhydrous dichloromethane are mixed, stirred at room temperature for 15-20 minutes, and heated to reflux temperature for 15 minutes. After the reaction is completed, the reaction mixture is washed and dried to obtain a flame retardant containing carbon-carbon double bonds; Step A2: 4-bromo-1-butene, anhydrous toluene and chloroplatinic acid solution were mixed, nitrogen was introduced, and the mixture was preheated at 60° C. for 60 min, triethoxysilane was added dropwise at 95° C., and the mixture was refluxed for 8 h. After the reaction was completed, the reaction product was washed with water, separated, dried, filtered, and rotary evaporated to obtain bromobutyltriethoxysilane; Step A3: dimethylaminoethyl methacrylate, bromobutyltriethoxysilane and acetone are mixed, nitrogen is introduced, the mixture is reacted at 55° C. for 60 hours, and the acetone is removed by reduced pressure distillation to obtain a distillate; the remaining distillate is cooled to room temperature, ether is added, the mixture is cooled to 0° C. for crystallization, suction filtered, washed and dried to obtain an antibacterial siloxane monomer; Step A4: Mix a flame retardant containing a carbon-carbon double bond, an antibacterial siloxane monomer, 1-dodecene and water, introduce nitrogen while stirring, heat to 65° C. after 30 minutes, drop 0.3wt% azobisisobutylamidine hydrochloride solution, react at 65° C. for 8-10 hours to obtain a reaction solution; cool the reaction solution to room temperature and pour it into acetone, filter, crush, wash, and dry to obtain a modified siloxane polymer.

3. A water-resistant protective film according to claim 2, characterized in that: In step A1, the usage ratio of DOPO-HQ, undecenoyl chloride, pyrimidine and anhydrous dichloromethane is 5 g:6.5 g:4 mL:125 mL.

4. The water-resistant protective film according to claim 2, characterized in that: In step A2, the usage ratio of 4-bromo-1-butene, anhydrous toluene, chloroplatinic acid solution, and triethoxysilane is 6.5 g:18 g:100 μL:9 g; the usage ratio of chloroplatinic acid and isopropanol in the chloroplatinic acid solution is 0.25 g:25 mL.

5. The water-resistant protective film according to claim 2, characterized in that: In step A3, the mass ratio of dimethylaminoethyl methacrylate, bromobutyltriethoxysilane and acetone is 6:14.5:

30.

6. The water-resistant protective film according to claim 2, characterized in that: In step A4, the amount ratio of the flame retardant containing carbon-carbon double bonds, the antibacterial siloxane monomer, 1-dodecene, water, and 0.3 wt % azobisisobutyramidine hydrochloride solution is 6.57 g: 0.78 g: 0.08 g: 32 mL: 13 mL.

7. The water-resistant protective film according to claim 1, characterized in that: The antioxidant is at least one of the antioxidant 1010 , the antioxidant 2246 , the antioxidant 1076 , and the antioxidant 330 .

8. A method for preparing a water-resistant protective film according to any one of claims 1 to 7, characterized in that: The following steps are involved: Weigh polyethylene terephthalate, modified siloxane polymer and antioxidant, mix and stir evenly in a high-speed mixer, then melt them on a twin-screw extruder, and then extrude and cast them into a film in an extrusion casting machine at an extrusion temperature of 260-280° C. to obtain a washable protective film.

9. The method for preparing a water-washable protective film according to claim 8, characterized in that: The temperature of each section of the twin-screw extruder is 270-290°C, and the screw speed is 80-100r / min.

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