A high-transmittance protective film for dimming film and preparation method thereof

Abstract

The invention discloses a high-transmittance protective film for dimming film and a preparation method thereof. The hydroxyl group on modified polyethylene and the hydroxyl group on the modified polyester side chain are respectively reacted with the isocyanate group on diphenylmethyl diisocyanate, and finally extruded and blown into a film. The modifier molecule contains intramolecular hydrogen bonds formed by carbonyl groups and hydroxyl groups, forming an intramolecular six-membered ring containing hydrogen bonds, which has a relatively stable conjugated structure. After absorbing ultraviolet rays, molecular thermal motion can occur, and the internal hydrogen bonds are broken, and the ultraviolet energy is released in the form of heat energy. At the same time, the hydroxyl groups on the benzene ring and the adjacent nitrogen atoms can also form intramolecular hydrogen bonds to form a six-membered chelate ring, thereby enhancing the ultraviolet resistance of the protective film. The molecule contains organic silicon segments and a large number of benzene rings, and the polyethylene molecular chain and the polyester molecular chain are grafted, thereby further improving the aging resistance of the protective film, preventing the protective film from yellowing, and maintaining the high-transmittance effect.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing a dimming film protective film, and in particular to a high-transmittance protective film for a dimming film and a preparation method thereof. Background Art

[0002] With the development of human society, people's demand for smart materials has greatly increased. Smart materials are new materials that can sense changes in the surrounding environment and take corresponding countermeasures to environmental changes. Among various types of smart materials, stimulus-responsive materials are one of the important branches. Polymer dispersed liquid crystal refers to a composite material formed by micron-sized liquid crystal droplets uniformly dispersed in a polymer matrix. This composite material has both the mechanical properties of polymers and the photoelectric properties of liquid crystals. The dimming film is a smart dimming film prepared by sandwiching polymer dispersed liquid crystals between two layers of transparent electrodes and has the ability to adjust the transmittance of visible light. In order to protect the dimming film from damage, a protective film will be attached to the surface of the dimming film. Some protective films will turn yellow after long-term exposure to light, which seriously affects the appearance of the dimming film. Summary of the invention

[0003] The purpose of the present invention is to provide a high-transmittance protective film for a dimming film and a preparation method thereof, which solves the problem that the current high-transmittance protective film turns yellow after long-term use, affecting the transmittance.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A method for preparing a high-transmittance protective film for a dimming film is prepared by the following steps:

[0006] Step A1: 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, a modifier and tetrabutyl titanate are uniformly mixed, and reacted for 2-3 hours at a speed of 60-80 r / min, a temperature of 235-237° C. and a pressure of 0.25-0.30 MPa, and further reacted for 2-3 hours at a temperature of 260-265° C. and a pressure of 100-110 Pa to obtain a modified polyester;

[0007] Step A2: N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide are mixed and added to a twin-screw extruder. Under the conditions of a rotation speed of 60-120r / min and a temperature of 160-170°C, the mixture is extruded and granulated to obtain modified polyethylene. The modified polyethylene, modified polyester and diphenylmethyl diisocyanate are mixed and added to a twin-screw extruder. Under the conditions of a rotation speed of 60-120r / min and a temperature of 180-190°C, the mixture is extruded and blown into a film to obtain a high-transmittance protective film for dimming film.

[0008] Furthermore, the mass ratio of 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, modifier and tetrabutyl titanate described in step A1 is 103.14:70.21:54.1:2.44:12.3:0.22.

[0009] Furthermore, the mass ratio of N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide described in step A2 is 10:100:0.3, the polyethylene is linear low-density polyethylene 7144, the mass ratio of modified polyethylene, modified polyester and diphenylmethyl diisocyanate is 16:24:3, and the blow molding ratio of the film is 2.5.

[0010] Further, the modifier is prepared by the following steps:

[0011] Step B1: uniformly mix cyanuric chloride, resorcinol, dioxane and aluminum chloride, and react for 2-3 hours at a speed of 150-200 r / min and a temperature of 25-30° C. to obtain intermediate 1; uniformly mix intermediate 1, vinyl bromide and acetone, and stir and reflux for 5-10 minutes at a speed of 200-300 r / min and a temperature of 60-70° C., add sodium carbonate, and react for 10-15 hours to obtain intermediate 2;

[0012] Step B2: The intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and acetone are uniformly mixed, and potassium carbonate is added under the conditions of a rotation speed of 300-500 r / min and a temperature of 80-90° C., and the mixture is reacted for 3-5 hours to obtain the intermediate 3. Diphenyldichlorosilane and deionized water are mixed, and the mixture is stirred for 10-15 minutes under the conditions of a rotation speed of 200-300 r / min and a temperature of 40-50° C., and concentrated sulfuric acid is added and the temperature is raised to 60-70° C., and 1,1,3,3-tetramethyldisiloxane is added, and the mixture is reacted for 3-5 hours to obtain the hydrogen-terminated polysiloxane;

[0013] Step B3: Mix the hydrogen-terminated polysiloxane, intermediate 3 and DMF evenly, stir and add chloroplatinic acid at a speed of 200-300 r / min and a temperature of 60-70°C, react for 4-6 hours, add 3-butene-1-ol, and continue to react for 4-6 hours to obtain a modifier.

[0014] Furthermore, the molar ratio of cyanuric chloride, resorcinol and aluminum chloride in step B1 is 2:4:3, and the usage ratio of intermediate 1, vinyl bromide and sodium carbonate is 50mmol:100mmol:7g.

[0015] Furthermore, the amount ratio of the intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and potassium carbonate described in step B2 is 50mmol:25mmol:3g, the amount ratio of diphenyldichlorosilane, deionized water and 1,1,3,3-tetramethyldisiloxane is 5mmol:20mL:3mmol, and the amount of concentrated sulfuric acid is 5-8% of the total mass of diphenyldichlorosilane and 1,1,3,3-tetramethyldisiloxane.

[0016] Furthermore, the molar ratio of the terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol described in step B3 is n:3n+1:2n+2, n is a natural number greater than 0, and the concentration of chloroplatinic acid in the mixture of terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol is 30-35 ppm.

[0017] Beneficial effects of the present invention: The high-transmittance protective film for dimming film prepared by the present invention is prepared by esterification polymerization with 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol and a modifier as raw materials to prepare a modified polyester, N-(2-hydroxyethyl)maleimide and polyethylene are extruded to make the double bond of the side chain of N-(2-hydroxyethyl)maleimide grafted with the main chain of polyethylene to prepare a modified polyethylene, and the modified polyethylene, the modified polyester and diphenylmethyl diisocyanate are extruded to make the hydroxyl groups on the modified polyethylene and the side chains of the modified polyester The hydroxyl groups of the cyanuric chloride react with the isocyanate groups on diphenylmethyl diisocyanate respectively, and finally extrude and blow mold into a film. The modifier uses cyanuric chloride and resorcinol as raw materials and controls the temperature so that the two chlorine atoms on cyanuric chloride react with the 4th position of resorcinol to obtain intermediate 1. Intermediate 1 is reacted with vinyl bromide so that the bromine atom on the vinyl bromide reacts with the 1st position phenolic hydroxyl group of intermediate 1 to obtain intermediate 2. Intermediate 2 is reacted with 2,2',4,4'-tetrahydroxybenzophenone so that the remaining chlorine atoms on the original cyanuric chloride react with The phenolic hydroxyl group on 4,4'-tetrahydroxybenzophenone is reacted to obtain intermediate 3, diphenyldichlorosilane is hydrolyzed, and then polymerized with 1,1,3,3-tetramethyldisiloxane to obtain terminal hydrogen polysiloxane, the terminal hydrogen polysiloxane and intermediate 3 are reacted to make the Si-H bond on the terminal hydrogen polysiloxane react with the double bond on intermediate 3, and the Si-H terminated hyperbranched structure is formed by controlling the dosage, and 3-butene-1-ol is added to terminate the hyperbranched alcohol to obtain a modifier, the modifier molecule contains intramolecular hydrogen bonds formed by carbonyl and hydroxyl groups, and the structure It forms an intramolecular six-membered ring containing hydrogen bonds and has a relatively stable conjugated structure. After absorbing ultraviolet rays, it can undergo molecular thermal motion, break the internal hydrogen bonds, and release the ultraviolet energy in the form of heat energy. At the same time, the hydroxyl group on the benzene ring and the adjacent nitrogen atom can also form intramolecular hydrogen bonds to form a six-membered chelate ring, which enhances the ultraviolet resistance of the protective film. The molecule contains silicone segments and a large number of benzene rings, and grafts polyethylene molecular chains and polyester molecular chains, which further improves the aging resistance of the protective film, prevents the protective film from yellowing, and maintains a high transmittance effect. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0019] Example 1

[0020] A method for preparing a high-transmittance protective film for a dimming film is prepared by the following steps:

[0021] Step A1: 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, a modifier and tetrabutyl titanate are uniformly mixed, and reacted for 2 hours at a speed of 60 r / min, a temperature of 235° C. and a pressure of 0.25 MPa, and then reacted for 2 hours at a temperature of 260° C. and a pressure of 100 Pa to obtain a modified polyester;

[0022] Step A2: N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide are mixed, added to a twin-screw extruder, and extruded into granules at a speed of 60 r / min and a temperature of 160°C to obtain modified polyethylene. The modified polyethylene, modified polyester and diphenylmethyl diisocyanate are mixed and added to a twin-screw extruder. At a speed of 60 r / min and a temperature of 180°C, they are extruded and blown into a film to obtain a high-transmittance protective film for dimming film.

[0023] The mass ratio of 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, modifier and tetrabutyl titanate described in step A1 is 103.14:70.21:54.1:2.44:12.3:0.22.

[0024] The mass ratio of N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide described in step A2 is 10:100:0.3, the polyethylene is linear low-density polyethylene 7144, the mass ratio of modified polyethylene, modified polyester and diphenylmethyl diisocyanate is 16:24:3, and the blow molding ratio of the film is 2.5.

[0025] The modifier is prepared by the following steps:

[0026] Step B1: Cyanuric chloride, resorcinol, dioxane and aluminum chloride are mixed evenly, and reacted at a speed of 150 r / min and a temperature of 25° C. for 2 h to obtain intermediate 1; intermediate 1, vinyl bromide and acetone are mixed evenly, and stirred and refluxed at a speed of 200 r / min and a temperature of 60° C. for 5 min, sodium carbonate is added, and the reaction is carried out for 10 h to obtain intermediate 2;

[0027] Step B2: The intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and acetone were mixed uniformly, stirred at a speed of 300 r / min and a temperature of 80°C, and potassium carbonate was added to react for 3 hours to obtain the intermediate 3. Diphenyldichlorosilane and deionized water were mixed, stirred at a speed of 200 r / min and a temperature of 40°C for 10 minutes, concentrated sulfuric acid was added and the temperature was raised to 60°C, 1,1,3,3-tetramethyldisiloxane was added, and the reaction was carried out for 3 hours to obtain the hydrogen-terminated polysiloxane;

[0028] Step B3: Mix the hydrogen-terminated polysiloxane, intermediate 3 and DMF evenly, stir and add chloroplatinic acid at a speed of 200 r / min and a temperature of 60°C, react for 4 hours, add 3-butene-1-ol, and continue to react for 4 hours to obtain a modifier.

[0029] The molar ratio of cyanuric chloride, resorcinol and aluminum chloride in step B1 is 2:4:3, and the amount ratio of intermediate 1, vinyl bromide and sodium carbonate is 50mmol:100mmol:7g.

[0030] The amount ratio of intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and potassium carbonate described in step B2 is 50mmol:25mmol:3g, the amount ratio of diphenyldichlorosilane, deionized water and 1,1,3,3-tetramethyldisiloxane is 5mmol:20mL:3mmol, and the amount of concentrated sulfuric acid is 5% of the total mass of diphenyldichlorosilane and 1,1,3,3-tetramethyldisiloxane.

[0031] The molar ratio of the terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol described in step B3 is 1:4:4, and the concentration of chloroplatinic acid in the mixture of terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol is 30 ppm.

[0032] Example 2

[0033] A method for preparing a high-transmittance protective film for a dimming film is prepared by the following steps:

[0034] Step A1: 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, a modifier and tetrabutyl titanate are uniformly mixed, and reacted for 2.5 hours at a speed of 60 r / min, a temperature of 236° C. and a pressure of 0.28 MPa, and then reacted for 2.5 hours at a temperature of 260° C. and a pressure of 105 Pa to obtain a modified polyester;

[0035] Step A2: N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide are mixed, added to a twin-screw extruder, and extruded into granules at a speed of 60 r / min and a temperature of 165°C to obtain modified polyethylene. The modified polyethylene, modified polyester and diphenylmethyl diisocyanate are mixed and added to a twin-screw extruder. At a speed of 60 r / min and a temperature of 185°C, they are extruded and blown into a film to obtain a high-transmittance protective film for dimming film.

[0036] The mass ratio of 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, modifier and tetrabutyl titanate described in step A1 is 103.14:70.21:54.1:2.44:12.3:0.22.

[0037] The mass ratio of N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide described in step A2 is 10:100:0.3, the polyethylene is linear low-density polyethylene 7144, the mass ratio of modified polyethylene, modified polyester and diphenylmethyl diisocyanate is 16:24:3, and the blow molding ratio of the film is 2.5.

[0038] The modifier is prepared by the following steps:

[0039] Step B1: Cyanuric chloride, resorcinol, dioxane and aluminum chloride were mixed evenly, and reacted at a speed of 150 r / min and a temperature of 28° C. for 2.5 hours to obtain intermediate 1; intermediate 1, vinyl bromide and acetone were mixed evenly, and stirred and refluxed at a speed of 200 r / min and a temperature of 65° C. for 8 minutes, and sodium carbonate was added, and the reaction was carried out for 13 hours to obtain intermediate 2;

[0040] Step B2: The intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and acetone were mixed uniformly, stirred at a speed of 300 r / min and a temperature of 85°C, and potassium carbonate was added to react for 4 hours to obtain the intermediate 3. Diphenyldichlorosilane and deionized water were mixed, stirred at a speed of 200 r / min and a temperature of 45°C for 13 minutes, concentrated sulfuric acid was added and the temperature was raised to 65°C, 1,1,3,3-tetramethyldisiloxane was added, and the reaction was carried out for 4 hours to obtain the hydrogen-terminated polysiloxane;

[0041] Step B3: Mix the hydrogen-terminated polysiloxane, intermediate 3 and DMF evenly, stir and add chloroplatinic acid at a speed of 200 r / min and a temperature of 65°C, react for 5 hours, add 3-butene-1-ol, and continue to react for 5 hours to obtain a modifier.

[0042] The molar ratio of cyanuric chloride, resorcinol and aluminum chloride in step B1 is 2:4:3, and the amount ratio of intermediate 1, vinyl bromide and sodium carbonate is 50mmol:100mmol:7g.

[0043] The amount ratio of intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and potassium carbonate described in step B2 is 50mmol:25mmol:3g, the amount ratio of diphenyldichlorosilane, deionized water and 1,1,3,3-tetramethyldisiloxane is 5mmol:20mL:3mmol, and the amount of concentrated sulfuric acid is 7% of the total mass of diphenyldichlorosilane and 1,1,3,3-tetramethyldisiloxane.

[0044] The molar ratio of the terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol described in step B3 is 2:7:6, and the concentration of chloroplatinic acid in the mixture of terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol is 33 ppm.

[0045] Example 3

[0046] A method for preparing a high-transmittance protective film for a dimming film is prepared by the following steps:

[0047] Step A1: 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, a modifier and tetrabutyl titanate are uniformly mixed, and reacted for 3 hours at a speed of 80 r / min, a temperature of 237° C. and a pressure of 0.30 MPa, and further reacted for 3 hours at a temperature of 265° C. and a pressure of 110 Pa to obtain a modified polyester;

[0048] Step A2: Mix N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide, add them to a twin-screw extruder, and extrude and granulate them at a speed of 120r / min and a temperature of 170°C to obtain modified polyethylene. Mix the modified polyethylene, modified polyester and diphenylmethyl diisocyanate and add them to a twin-screw extruder. At a speed of 120r / min and a temperature of 190°C, extrude and blow mold them into a film to obtain a high-transmittance protective film for dimming film.

[0049] The mass ratio of 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, modifier and tetrabutyl titanate described in step A1 is 103.14:70.21:54.1:2.44:12.3:0.22.

[0050] The mass ratio of N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl oxide described in step A2 is 10:100:0.3, the polyethylene is linear low-density polyethylene 7144, the mass ratio of modified polyethylene, modified polyester and diphenylmethyl diisocyanate is 16:24:3, and the blow molding ratio of the film is 2.5.

[0051] The modifier is prepared by the following steps:

[0052] Step B1: Cyanuric chloride, resorcinol, dioxane and aluminum chloride are mixed evenly, and reacted at a speed of 200 r / min and a temperature of 30° C. for 3 h to obtain intermediate 1; intermediate 1, vinyl bromide and acetone are mixed evenly, and stirred and refluxed at a speed of 300 r / min and a temperature of 70° C. for 10 min, sodium carbonate is added, and the reaction is carried out for 15 h to obtain intermediate 2;

[0053] Step B2: The intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and acetone were mixed uniformly, stirred at a speed of 500 r / min and a temperature of 90°C, and potassium carbonate was added to react for 5 hours to obtain the intermediate 3. Diphenyldichlorosilane and deionized water were mixed, stirred at a speed of 300 r / min and a temperature of 50°C for 15 minutes, concentrated sulfuric acid was added and the temperature was raised to 70°C, and 1,1,3,3-tetramethyldisiloxane was added to react for 5 hours to obtain the hydrogen-terminated polysiloxane;

[0054] Step B3: Mix the hydrogen-terminated polysiloxane, intermediate 3 and DMF evenly, stir and add chloroplatinic acid at a speed of 300 r / min and a temperature of 70°C, react for 6 hours, add 3-butene-1-ol, and continue to react for 6 hours to obtain a modifier.

[0055] The molar ratio of cyanuric chloride, resorcinol and aluminum chloride in step B1 is 2:4:3, and the amount ratio of intermediate 1, vinyl bromide and sodium carbonate is 50mmol:100mmol:7g.

[0056] The amount ratio of intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and potassium carbonate described in step B2 is 50mmol:25mmol:3g, the amount ratio of diphenyldichlorosilane, deionized water and 1,1,3,3-tetramethyldisiloxane is 5mmol:20mL:3mmol, and the amount of concentrated sulfuric acid is 8% of the total mass of diphenyldichlorosilane and 1,1,3,3-tetramethyldisiloxane.

[0057] The molar ratio of the terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol described in step B3 is 3:10:8, and the concentration of chloroplatinic acid in the mixture of terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol is 35 ppm.

[0058] Comparative Example 1

[0059] Compared with Example 1, no modifier was added in this comparative example, and the remaining steps were the same.

[0060] Comparative Example 2

[0061] Compared with Example 1, this comparative example uses hydrogen-terminated polysiloxane, 3-butene-1-ol and DMF to mix evenly, stir and add chloroplatinic acid at a speed of 200 r / min and a temperature of 60° C., and react for 4 hours. The product replaces the modifier, and the remaining steps are the same.

[0062] The high-transmittance protective films prepared in Examples 1-3 and Comparative Examples 1-2 were made into samples of 10cm×10cm×2cm and irradiated with light of 600nm wavelength. The transmission spectrum was measured by a spectrometer to obtain the transmittance. The samples were then placed in a 340nm UV light box and irradiated continuously at 60°C for 240h. The transmittance was tested again. The test results are shown in the following table.

[0063]

[0064] It can be seen from the above table that the present application still has good light transmittance after light aging.

[0065] The above contents are merely examples and explanations of the concept of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-transmittance protective film for a dimming film, characterized in that: Made by the following steps: Step A1: 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, a modifier and tetrabutyl titanate are mixed and reacted to prepare a modified polyester; Step A2: N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl peroxide are mixed, added into a twin-screw extruder, extruded into granules, and modified polyethylene is obtained; the modified polyethylene, modified polyester and diphenylmethyl diisocyanate are mixed and added into a twin-screw extruder, extruded and blown into a film, and a high-transmittance protective film for dimming film is obtained; The mass ratio of N-(2-hydroxyethyl)maleimide, polyethylene and dibenzoyl peroxide in step A2 is 10:100:0.3, the polyethylene is linear low-density polyethylene 7144, the mass ratio of modified polyethylene, modified polyester and diphenylmethyl diisocyanate is 16:24:3, and the blow ratio of the blown film is 2.5; The modifier is prepared by the following steps: Step B1: cyanuric chloride, resorcinol, dioxane and aluminum chloride are mixed and reacted to obtain intermediate 1, intermediate 1, vinyl bromide and acetone are mixed and stirred under reflux, sodium carbonate is added, and reacted to obtain intermediate 2; Step B2: Mix and stir the intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and acetone, add potassium carbonate, and react to obtain the intermediate 3; mix diphenyldichlorosilane and deionized water, stir, add concentrated sulfuric acid and heat, add 1,1,3,3-tetramethyldisiloxane, and react to obtain the hydrogen-terminated polysiloxane; Step B3: The hydrogen-terminated polysiloxane, intermediate 3 and DMF are mixed and stirred, and chloroplatinic acid is added. After the reaction, 3-butene-1-ol is added and the reaction is continued to obtain a modifier.

2. The method for preparing a high-transmittance protective film for a dimming film according to claim 1, characterized in that: The mass ratio of 1,4-cyclohexanedicarboxylic acid, 1,4-cyclohexanedimethanol, polybutylene glycol 1000, butanediol, modifier and tetrabutyl titanate described in step A1 is 103.14:70.21:54.1:2.44:12.3:0.

22.

3. The method for preparing a high-transmittance protective film for a dimming film according to claim 1, characterized in that: The molar ratio of cyanuric chloride, resorcinol and aluminum chloride in step B1 is 2:4:3, and the amount ratio of intermediate 1, vinyl bromide and sodium carbonate is 50mmol:100mmol:7g.

4. The method for preparing a high-transmittance protective film for a dimming film according to claim 1, characterized in that: The amount ratio of intermediate 2, 2,2',4,4'-tetrahydroxybenzophenone and potassium carbonate described in step B2 is 50mmol:25mmol:3g, the amount ratio of diphenyldichlorosilane, deionized water and 1,1,3,3-tetramethyldisiloxane is 5mmol:20mL:3mmol, and the amount of concentrated sulfuric acid is 5-8% of the total mass of diphenyldichlorosilane and 1,1,3,3-tetramethyldisiloxane.

5. The method for preparing a high-transmittance protective film for a dimming film according to claim 1, characterized in that: The molar ratio of the terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol described in step B3 is n:3n+1:2n+2, n is a natural number greater than 0, and the concentration of chloroplatinic acid in the mixture of terminal hydrogen polysiloxane, intermediate 3 and 3-butene-1-ol is 30-35ppm.

6. A high-transmittance protective film for a dimming film, characterized in that: Prepared according to any one of the preparation methods described in claims 1-5.

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