Functional PET polyurethane protective film and preparation method thereof

Abstract

The invention relates to the technical field of protective films, and provides a functional PET polyurethane protective film and a preparation method thereof.The protective film sequentially comprises a PET base material layer, an antistatic coating, a PU glue coating and a release layer from bottom to top; wherein the antistatic coating is prepared from the following raw materials in parts by weight: 40 to 70 parts of waterborne polyurethane, 3 to 9 parts of a modified quaternary ammonium salt type antistatic agent, 8 to 15 parts of modified kaolin, 1 to 2 parts of a silane coupling agent, 0.2 to 0.8 part of a catalyst, 0.2 to 1 part of a waterborne flatting agent, 5 to 15 parts of deionized water and 6 to 14 parts of a curing agent. The protective film disclosed by the invention is produced by coating in a dust-free room environment, a laminated product has no residue after high temperature and high humidity, and the protective film has the characteristics of high cleanliness, good flatness, good exhaust property, good weather resistance and good antistatic property.

Description

Technical Field

[0001] The invention belongs to the technical field of protective films, and particularly relates to a functional PET polyurethane protective film and a preparation method thereof. Background Art

[0002] In today's society, with the continuous advancement of science and technology, the application of optical products such as display screens and touch screens is becoming more and more extensive, and the demand for surface protection is also growing. For precision electronic devices such as smart phones, tablets, laptops, etc., the protection of their screens is particularly important. Only by coating and producing in a clean room environment to ensure the cleanliness and product quality of the protective film can the high requirements of precision electronic equipment for protective films be met.

[0003] PET polyurethane protective film not only needs to have basic protective functions, but also needs to have antistatic, high temperature and high humidity resistance and other characteristics. At the same time, environmental protection has become an important theme in today's society, and water-based protective film is favored for its environmental protection characteristics. Therefore, by improving water-based polyurethane to prepare a protective film that is both environmentally friendly and has good protective performance, it can meet the pursuit of environmental protection and sustainable development in modern society.

[0004] Chinese patent CN 108949052 A discloses an antistatic and high temperature resistant TPU protective film tape and its preparation method, comprising a transparent base film, an antistatic layer, a polyurethane adhesive layer and a single-sided release film. The polyurethane adhesive layer comprises 30%-70% of a polyurethane adhesive, 10‰-30‰ of an antistatic agent, 0.1‰-8‰ of a curing additive and 0.1‰-1‰ of a catalytic additive. The protective film tape in this invention not only has stable adhesion, but also has an antistatic value of up to 10%. 8 -10 10 , which can ensure a better antistatic effect; however, the polyurethane adhesive layer in the protective film of this invention uses ethyl acetate as a solvent, which has low toxicity and does not meet environmental protection requirements.

[0005] Therefore, there is an urgent need for a functional PET polyurethane protective film that meets environmental protection requirements and has excellent antistatic properties and weather resistance. Summary of the invention

[0006] In view of the existing technical problems, the purpose of the present invention is to provide a functional PET polyurethane protective film and a preparation method thereof. The protective film of the present invention is produced by coating in a clean room environment, has no residue after being bonded to the product under high temperature and high humidity, and has the characteristics of high cleanliness, good flatness, good air exhaust, good weather resistance, and good antistatic properties.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] On one hand, the present invention provides a functional PET polyurethane protective film, which comprises a PET substrate layer, an antistatic coating, a polyurethane glue coating and a release layer from bottom to top; wherein:

[0009] The antistatic coating comprises the following raw materials, measured by weight: 40-70 parts of waterborne polyurethane, 3-9 parts of modified quaternary ammonium salt antistatic agent, 8-15 parts of modified kaolin, 1-2 parts of silane coupling agent, 0.2-0.8 parts of catalyst, 0.2-1 parts of waterborne leveling agent, 5-15 parts of deionized water, and 6-14 parts of curing agent.

[0010] The reaction mechanism and effects of the present invention are as follows:

[0011] 1. Modified quaternary ammonium salt antistatic agent is a new type of high-performance antistatic agent with the ability to reduce frictional static electricity. It forms a "core-shell structure" in the polymer matrix and forms a network or layered distribution on the polymer surface to form a conductive network. Its ions easily aggregate in the system to form chemical cross-linking points, which can greatly improve its antistatic performance and thus reduce the impact of ambient temperature and humidity on the surface resistivity of the material.

[0012] The invention uses lactobionic acid and 4-pentene-1-amine as raw materials to form an amide bond through an amine ester reaction, and then polymerizes with styrene, 1-vinyl imidazole, and methacryloyloxyethyl trimethyl ammonium chloride to form a modified quaternary ammonium salt type antistatic agent. The modified quaternary ammonium salt type antistatic agent of the invention integrates amide, benzene ring, imidazole, quaternary ammonium salt and sugar base into one, and has excellent antistatic performance. On the one hand, the benzene ring, imidazole and amide structure make the modified quaternary ammonium salt type antistatic agent have good thermal stability; on the other hand, the lactobionic acid structure contains multiple hydroxyls, which improves the hydrophilicity and makes it more evenly dispersed in the coating raw material, thereby improving the antistatic property of the antistatic coating as a whole.

[0013] 2. Kaolin can not only improve the wear resistance, chemical corrosion resistance and scratch resistance of the coating, but also enhance the thermal stability of the coating, so that it can maintain good performance at higher temperatures; however, kaolin may agglomerate in the coating.

[0014] The present invention first uses dopamine hydrochloride to self-polymerize to modify kaolin, and then further sulfonates with dimethylpropyl sulfonamide ethyl methacrylate through Michael addition reaction to improve the anti-pollution ability of the antistatic coating, and the cleanliness is high. Furthermore, the applicant modifies the obtained solid by coupling agent, so that the modified kaolin is evenly dispersed, the adhesion of the two-phase interface is improved, and suitable peeling force and removability are obtained; in addition, the modified kaolin further improves the weather resistance of the coating.

[0015] In some embodiments, the preparation method of the modified quaternary ammonium salt antistatic agent comprises the following steps:

[0016] S1. Add lactobionic acid, methanol and 4-penten-1-amine to a reaction kettle, heat to react, stand to cool, rotary evaporate, wash, filter and vacuum dry to obtain an intermediate product;

[0017] S2. The intermediate product obtained in step S1, styrene, 1-vinylimidazole, methacryloyloxyethyltrimethylammonium chloride, anhydrous ethanol and water are mixed, an inert gas is introduced, stirred, an initiator is added, heated to 75-85°C for reaction for 5-6h, cooled, added dropwise to n-hexane for precipitation, and vacuum dried to obtain a modified quaternary ammonium salt antistatic agent.

[0018] In some embodiments, the molar ratio of lactobionic acid to 4-penten-1-amine in step S1 is 1:

[0019] (1.1-1.4).

[0020] In some embodiments, the molar ratio of the intermediate product, styrene, 1-vinylimidazole, and methacryloyloxyethyltrimethylammonium chloride in step S2 is 1:(0.5-0.8):(0.7-1):(1-1.3).

[0021] In some embodiments, the method for preparing modified kaolin comprises the following steps:

[0022] A1. Mix deionized water, anhydrous ethanol and hydroxylamine hydrochloride, add kaolin, stir, then add tris(hydroxymethyl)aminomethane hydrochloride and dopamine hydrochloride in sequence, stir to react, wash, filter, dry and grind to obtain a product;

[0023] A2. The product obtained in step A1 is dispersed in deionized water, ultrasonically treated, dimethylpropyl sulfonamide ethyl methacrylate is added, heated to 50-60 ° C for 18-24 h, centrifuged, washed, and dried to obtain a solid;

[0024] A3. The solid obtained in step A2, the coupling agent, deionized water and anhydrous ethanol are mixed, heated to 75-85°C and stirred for 3-4h, centrifuged, washed and dried to obtain modified kaolin.

[0025] In some embodiments, the mass ratio of kaolin and dopamine hydrochloride in step A1 is 1:

[0026] (0.015-0.04).

[0027] In some embodiments, the mass ratio of the solid to the coupling agent in step A3 is 10:(0.6-1).

[0028] In some embodiments, the mass ratio of the product in step A2 to dimethylpropylsulfonamide ethyl methacrylate is 1:(0.2-0.5).

[0029] In some embodiments, the curing agent is selected from any one or more of diisocyanate, diisocyanate dimer and diisocyanate trimer.

[0030] In some embodiments, the thickness of the PET substrate layer is 50-80 μm, the thickness of the antistatic coating is 50-70 μm, the thickness of the polyurethane glue coating is 40-60 μm, and the thickness of the release layer is 45-55 μm.

[0031] In some embodiments, the catalyst is selected from any one or more of dibutyltin dilaurate, stannous isooctanoate and triethylenediamine.

[0032] In some embodiments, the silane coupling agent is triacetoxyvinylsilane.

[0033] In some embodiments, the polyurethane glue coating is a polyester polyurethane glue coating.

[0034] In some embodiments, the release layer is a PET release layer.

[0035] Another aspect of the present invention provides a method for preparing a functional PET polyurethane protective film, comprising the following steps:

[0036] 1. Mix waterborne polyurethane, modified quaternary ammonium salt antistatic agent, modified kaolin, silane coupling agent, catalyst, waterborne leveling agent, deionized water and curing agent and add them into a reaction kettle to obtain an antistatic adhesive;

[0037] 2. Applying polyurethane glue to the lower surface of the release layer using a coating machine, adjusting the thickness, and drying to obtain a polyurethane glue coating;

[0038] 3. applying the antistatic adhesive prepared in step 1 to the lower surface of the polyurethane glue coating prepared in step 2, adjusting the thickness, and drying to obtain an antistatic coating;

[0039] Fourth, compound the PET substrate layer on the lower surface of the antistatic coating prepared in step 3, cure it, and cut it to obtain a protective film.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. The protective film of the present invention is produced by coating in a clean room environment, and has no residue after being bonded to the product under high temperature and high humidity. It has the characteristics of high cleanliness, good flatness, good exhaust performance, good weather resistance, and good antistatic performance.

[0042] 2. The modified quaternary ammonium salt antistatic agent of the present invention integrates amide, benzene ring, imidazole, quaternary ammonium salt and sugar base, and has excellent antistatic performance and good thermal stability.

[0043] 3. The modified kaolin of the present invention improves the anti-pollution ability of the antistatic coating and has high cleanliness; further, the obtained solid is modified by a coupling agent so that the modified kaolin is evenly dispersed, suitable peeling force and removability are obtained, and the weather resistance of the coating is improved. DETAILED DESCRIPTION

[0044] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0045] Each protective film was prepared according to the ratio of each raw material and the preparation method specified in the following examples and comparative examples.

[0046] In order to facilitate those skilled in the art to implement the present invention, some raw material manufacturers of the embodiments and comparative examples are described as follows:

[0047] Isocyanate dimer: dimer acid diisocyanate, purchased from Hubei Jiahui Xingcheng Biotechnology Co., Ltd.;

[0048] Water-based leveling agent: purchased from Nanjing Qinghai Trading Co., Ltd., model number is UH-420;

[0049] Waterborne polyurethane: purchased from Qingdao Ruikesi New Material Technology Co., Ltd., model FS-WPU;

[0050] Polyurethane glue: purchased from Zibo Excellence Technology Development Co., Ltd., model T80;

[0051] Other raw materials are not specially specified and can be purchased from the market.

[0052] Preparation Example 1

[0053] The preparation method of modified quaternary ammonium salt antistatic agent A comprises the following steps:

[0054] S1. Add 0.2 mol lactobionic acid, 400 ml methanol and 0.25 mol 4-pentene-1-amine into a reaction kettle, heat to 150°C, reflux for 24 hours, cool to room temperature, remove the solvent by rotary evaporation, wash with ether three times, filter, and vacuum dry at 60°C for 5 hours to obtain an intermediate product;

[0055] S2. 0.16 mol of the intermediate product obtained in step S1, 0.104 mol of styrene, 0.136 mol of 1-vinylimidazole, 0.184 mol of methacryloyloxyethyltrimethylammonium chloride, 150 ml of anhydrous ethanol and 100 ml of water were mixed, nitrogen was introduced, stirred at 250 rpm for 20 min, 2 g of azobisisobutyronitrile was added, heated to 80 ° C for 6 h, cooled to room temperature, added dropwise to 600 ml of frozen n-hexane in a liquid state for precipitation, and vacuum dried at 80 ° C for 24 h to obtain a modified quaternary ammonium salt antistatic agent A.

[0056] Preparation Example 2

[0057] The preparation method of the modified quaternary ammonium salt antistatic agent B is the same as that of Preparation Example 1, except that the amount of lactobionic acid added in step S1 is 0.32 mol.

[0058] Preparation Example 3

[0059] The preparation method of the modified quaternary ammonium salt antistatic agent C is the same as that of Preparation Example 1, except that the amount of methacryloyloxyethyltrimethylammonium chloride added in step S2 is 0.128 mol.

[0060] Preparation Example 4

[0061] The preparation method of modified kaolin A comprises the following steps:

[0062] A1. Mix 100 ml of deionized water, 33.3 ml of anhydrous ethanol, and 1 g of hydroxylamine hydrochloride, add 6 g of kaolin, stir for 30 min, then add 0.2 g of tris(hydroxymethyl)aminomethane hydrochloride and 0.15 g of dopamine hydrochloride in sequence, stir and react for 10 h, wash with deionized water 3 times, filter, dry at 80 ° C for 5 h, grind to obtain the product;

[0063] A2. 2 g of the product obtained in step A1 was dispersed in 800 ml of deionized water, ultrasonically treated for 30 min, 0.7 g of dimethylpropyl sulfonamide ethyl methacrylate was added, heated to 55 ° C for 20 h, centrifuged, washed three times with deionized water, and dried at 80 ° C for 5 h to obtain a solid;

[0064] A3. Mix 1000 mg of the solid obtained in step A2, 80 mg of bis(dioctylpyrophosphate)ethylene titanate, 150 ml of deionized water and 50 ml of anhydrous ethanol, heat to 80°C and stir for 4 hours, centrifuge, wash three times with deionized water, and dry at 80°C for 6 hours to obtain modified kaolin A.

[0065] Preparation Example 5

[0066] The preparation method of modified kaolin B is the same as that of Preparation Example 4, except that the amount of dopamine hydrochloride added in step A1 is 0.06 g.

[0067] Preparation Example 6

[0068] The preparation method of modified kaolin C is the same as that of Preparation Example 4, except that the amount of bis(dioctylpyrophosphate)ethylene titanate added in step A3 is 56 mg.

[0069] Example 1

[0070] A functional PET polyurethane protective film, the protective film comprises a PET substrate layer, an antistatic coating, a polyurethane glue coating and a PET release layer from bottom to top; wherein:

[0071] The following raw materials are prepared for the antistatic coating in parts by weight: 55 parts of waterborne polyurethane, 6 parts of modified quaternary ammonium salt antistatic agent A, 11.5 parts of modified kaolin A, 1.5 parts of triacetoxyvinylsilane, 0.5 parts of dibutyltin dilaurate, 0.6 parts of waterborne leveling agent, 10 parts of deionized water, and 10 parts of dimer acid diisocyanate;

[0072] The thickness of the PET substrate layer is 60 μm, the thickness of the antistatic coating is 60 μm, the thickness of the polyurethane glue coating is 50 μm, and the thickness of the PET release layer is 50 μm.

[0073] The preparation method of the heat-reducing adhesive tape of this embodiment comprises the following steps:

[0074] 1. Mix waterborne polyurethane, modified quaternary ammonium salt antistatic agent A, modified kaolin A, silane coupling agent, catalyst, waterborne leveling agent, deionized water and curing agent and add them into a reaction kettle to obtain an antistatic adhesive;

[0075] 2. Use a coating machine to apply polyurethane glue to the lower surface of the release layer, adjust the thickness, and bake at 70° C. for 5 minutes to obtain a polyurethane glue coating;

[0076] 3. Apply the antistatic adhesive prepared in step 1 to the lower surface of the polyurethane glue coating prepared in step 2, adjust the thickness, and bake at 70° C. for 5 minutes to obtain an antistatic coating;

[0077] Fourth, the PET substrate layer is compounded on the lower surface of the antistatic coating prepared in step 3, aged at 45° C. for 48 hours, and cut to obtain a protective film.

[0078] Example 2

[0079] A functional PET polyurethane protective film, the protective film comprises a PET substrate layer, an antistatic coating, a polyurethane glue coating and a PET release layer from bottom to top; wherein:

[0080] The following raw materials are prepared for the antistatic coating in parts by weight: 40 parts of waterborne polyurethane, 3 parts of modified quaternary ammonium salt antistatic agent A, 8 parts of modified kaolin A, 1 part of triacetoxyvinylsilane, 0.2 parts of dibutyltin dilaurate, 0.2 parts of waterborne leveling agent, 5 parts of deionized water, and 6 parts of dimer acid diisocyanate;

[0081] The thickness of the PET substrate layer is 60 μm, the thickness of the antistatic coating is 60 μm, the thickness of the polyurethane glue coating is 50 μm, and the thickness of the PET release layer is 50 μm.

[0082] The preparation method of the protective film of this embodiment is the same as that of embodiment 1.

[0083] Example 3

[0084] A functional PET polyurethane protective film, the protective film comprises a PET substrate layer, an antistatic coating, a polyurethane glue coating and a PET release layer from bottom to top; wherein:

[0085] The antistatic coating is prepared by the following raw materials: 70 parts of waterborne polyurethane, 9 parts of modified quaternary ammonium salt antistatic agent A, 15 parts of modified kaolin A, 2 parts of triacetoxyvinylsilane, 0.8 parts of dibutyltin dilaurate, 1 part of waterborne leveling agent, 15 parts of deionized water, and 14 parts of dimer acid diisocyanate.

[0086] The thickness of the PET substrate layer is 60 μm, the thickness of the antistatic coating is 60 μm, the thickness of the polyurethane glue coating is 50 μm, and the thickness of the PET release layer is 50 μm.

[0087] The preparation method of the protective film of this embodiment is the same as that of embodiment 1.

[0088] Example 4

[0089] A functional PET polyurethane protective film and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified quaternary ammonium salt antistatic agent B is used to replace the modified quaternary ammonium salt antistatic agent A.

[0090] Example 5

[0091] A functional PET polyurethane protective film and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified quaternary ammonium salt antistatic agent C is used to replace the modified quaternary ammonium salt antistatic agent A.

[0092] Example 6

[0093] A functional PET polyurethane protective film and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified kaolin B is used to replace modified kaolin A.

[0094] Example 7

[0095] A functional PET polyurethane protective film and a preparation method thereof. The specific implementation manner is the same as that of Example 1, except that an equal amount of modified kaolin C is used to replace modified kaolin A.

[0096] Comparative Example 1

[0097] A functional PET polyurethane protective film and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of commercially available methacryloyloxyethyl trimethyl ammonium chloride is used to replace the modified quaternary ammonium salt antistatic agent A.

[0098] Comparative Example 2

[0099] A functional PET polyurethane protective film and a preparation method thereof, wherein the specific implementation manner is the same as that of Example 1, except that an equal amount of commercially available kaolin is used to replace modified kaolin A.

[0100] Effect evaluation:

[0101] The protective films prepared in the above-mentioned Examples 1-7 and Comparative Examples 1-2 were tested and analyzed, and the specific results are shown in Table 1.

[0102] Performance Testing:

[0103] (1) Antistatic test: refer to ASTMD257;

[0104] (2) Peel force test: Use a peel force tester to peel the prepared protective film at 50 N, 300 mm / min, and 180° to test the peel force and observe whether there is residual adhesive;

[0105] (3) High temperature and high humidity resistance test: The prepared protective film was placed in a 90°C oven for 24 hours, and then placed in an environment with a humidity of 80% for 24 hours. The protective film was observed for deformation, cracking, or glue release. If any of these conditions were found, the film was deemed unqualified.

[0106] Table 1

[0107] Serial number Antistatic value(Ω) Peel force (gf / inch) Is there any residual glue? High temperature and high humidity resistance Example 1 <![CDATA[9.8*10 9 ]]> 30 No residual glue qualified Example 2 <![CDATA[9.5*10 9 ]]> 29 No residual glue qualified Example 3 <![CDATA[9.7*10 9 ]]> 30 No residual glue qualified Example 4 <![CDATA[8.6*10 9 ]]> 28 No residual glue qualified Example 5 <![CDATA[8.2*10 9 ]]> 27 No residual glue qualified Example 6 <![CDATA[9.8*10 9 ]]> 35 No residual glue qualified Example 7 <![CDATA[9.7*10 9 ]]> 39 There is residual glue qualified Comparative Example 1 <![CDATA[7.5*10 9 ]]> 27 No residual glue qualified Comparative Example 2 <![CDATA[9.6*10 9 ]]> 41 There is residual glue Failure

[0108] From the results in Table 1, it can be seen that the protective films prepared in Examples 1-3 have good peeling force and good removability. At the same time, the protective films have good antistatic value and good weather resistance. After being placed in a high temperature and high humidity environment for 24 hours, there is still no deformation, cracking, glue coming out, etc.

[0109] Compared with Example 1, when preparing the modified quaternary ammonium salt antistatic agent, Example 4 changes the molar ratio of lactobionic acid and 4-penten-1-amine, and Example 5 changes the molar ratio of the intermediate product, styrene, 1-vinyl imidazole, and methacryloyloxyethyl trimethyl ammonium chloride, all of which affect the performance of the quaternary ammonium salt antistatic agent and weaken the antistatic value; while Comparative Example 1 replaces the modified quaternary ammonium salt antistatic agent A with an equal amount of commercially available methacryloyloxyethyl trimethyl ammonium chloride, and the antistatic effect is weak, which in turn affects the antistatic value of the protective film.

[0110] Compared with Example 1, when preparing modified kaolin, Example 6 changes the mass ratio of kaolin and dopamine hydrochloride, and Example 7 changes the mass ratio of polydopamine-modified kaolin and bis(dioctylpyrophosphate)ethylene titanate, both of which reduce the dispersibility and weather resistance of the modified kaolin, and thus affect the stripping force, residual glue removability and weather resistance; while Comparative Example 2 uses an equal amount of commercially available kaolin to replace modified kaolin A, resulting in agglomeration, which in turn affects the stripping force, residual glue removability and weather resistance.

[0111] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A functional PET polyurethane protective film, characterized in that: The protective film is composed of a PET substrate layer, an antistatic coating layer, a polyurethane glue coating layer and a release layer from bottom to top; wherein, The antistatic coating comprises the following raw materials, measured by weight: 40-70 parts of waterborne polyurethane, 3-9 parts of modified quaternary ammonium salt antistatic agent, 8-15 parts of modified kaolin, 1-2 parts of silane coupling agent, 0.2-0.8 parts of catalyst, 0.2-1 parts of waterborne leveling agent, 5-15 parts of deionized water, and 6-14 parts of curing agent.

2. A functional PET polyurethane protective film according to claim 1, characterized in that: The preparation method of the modified quaternary ammonium salt antistatic agent comprises the following steps: S1. Add lactobionic acid, methanol and 4-penten-1-amine to a reaction kettle, heat to react, stand to cool, rotary evaporate, wash, filter and vacuum dry to obtain an intermediate product; S2. The intermediate product obtained in step S1, styrene, 1-vinylimidazole, methacryloyloxyethyltrimethylammonium chloride, anhydrous ethanol and water are mixed, an inert gas is introduced, stirred, an initiator is added, heated to 75-85°C for reaction for 5-6h, cooled, added dropwise to n-hexane for precipitation, and vacuum dried to obtain a modified quaternary ammonium salt antistatic agent.

3. A functional PET polyurethane protective film according to claim 2, characterized in that: The molar ratio of lactobionic acid to 4-penten-1-amine in step S1 is 1:(1.1-1.4).

4. A functional PET polyurethane protective film according to claim 2, characterized in that: The molar ratio of the intermediate product, styrene, 1-vinylimidazole and methacryloyloxyethyltrimethylammonium chloride in step S2 is 1:(0.5-0.8):(0.7-1):(1-1.3).

5. A functional PET polyurethane protective film according to claim 1, characterized in that: The preparation method of the modified kaolin comprises the following steps: A1. Mix deionized water, anhydrous ethanol and hydroxylamine hydrochloride, add kaolin, stir, then add tris(hydroxymethyl)aminomethane hydrochloride and dopamine hydrochloride in sequence, stir to react, wash, filter, dry and grind to obtain a product; A2. The product obtained in step A1 is dispersed in deionized water, ultrasonically treated, dimethylpropyl sulfonamide ethyl methacrylate is added, heated to 50-60 ° C for 18-24 h, centrifuged, washed, and dried to obtain a solid; A3. The solid obtained in step A2, the coupling agent, deionized water and anhydrous ethanol are mixed, heated to 75-85°C and stirred for 3-4h, centrifuged, washed and dried to obtain modified kaolin.

6. A functional PET polyurethane protective film according to claim 5, characterized in that: The mass ratio of kaolin and dopamine hydrochloride in step A1 is 1:(0.015-0.04).

7. A functional PET polyurethane protective film according to claim 5, characterized in that: The mass ratio of the solid to the coupling agent in step A3 is 10:(0.6-1).

8. The functional PET polyurethane protective film according to claim 1, characterized in that: The curing agent is selected from any one or more of diisocyanate, diisocyanate dimer and diisocyanate trimer.

9. The functional PET polyurethane protective film according to claim 1, characterized in that: The thickness of the PET substrate layer is 50-80 μm, the thickness of the antistatic coating is 50-70 μm, the thickness of the polyurethane glue coating is 40-60 μm, and the thickness of the release layer is 45-55 μm.

10. A method for preparing the functional PET polyurethane protective film according to any one of claims 1 to 9, characterized in that: The following steps are included:

1. Mix waterborne polyurethane, modified quaternary ammonium salt antistatic agent, modified kaolin, silane coupling agent, catalyst, waterborne leveling agent, deionized water and curing agent and add them into a reaction kettle to obtain an antistatic adhesive; 2. Applying polyurethane glue to the lower surface of the release layer using a coating machine, adjusting the thickness, and drying to obtain a polyurethane glue coating; 3. applying the antistatic adhesive prepared in step 1 to the lower surface of the polyurethane glue coating prepared in step 2, adjusting the thickness, and drying to obtain an antistatic coating; Fourth, compound the PET substrate layer on the lower surface of the antistatic coating prepared in step 3, cure it, and cut it to obtain a protective film.