An anti-permeation car paint surface protection film and a preparation method thereof

Abstract

The application discloses an anti-permeation automobile paint surface protection film and a preparation method thereof, and relates to the technical field of paint surface protection films. The anti-permeation automobile paint surface protection film comprises a transparent base film, and a first coating layer and a second coating layer arranged on the surface of the transparent base film in sequence; the first coating layer is formed by epoxy resin modified polyurethane coating, and the second coating layer is formed by graphene modified polyurethane coating. The preparation method of the anti-permeation paint surface protection film is as follows: epoxy resin modified polyurethane coating is coated on one side of the transparent base film, once heating and curing and annealing are carried out, and the first coating layer is formed; graphene modified polyurethane coating is further coated on the side, twice heating and curing are carried out, ultraviolet light irradiation and drying are carried out, and the second coating layer is formed; and the anti-permeation automobile paint surface protection film is obtained. The automobile paint surface protection film prepared by the application has excellent wear resistance, tensile strength and anti-permeation while ensuring the light transmittance, and thus has excellent protection effect.

Description

Technical Field

[0001] This invention relates to the field of paint protection film technology, specifically an anti-penetration automotive paint protection film and its preparation method. Background Technology

[0002] With the continuous increase in car ownership, automotive paint protection film, as a product that can effectively protect the paint surface from external damage, is widely used. Polyurethane is often used as the base component of the protective film. Although it has certain protective and self-healing properties, its wear resistance is relatively average, which makes it easy to produce large scratches and difficult to self-repair. In addition, its anti-permeability is poor. In existing technologies, although some protective films are modified by adding nanomaterials to increase mechanical properties, the addition of some nanomaterials greatly reduces the light transmittance of the protective film, causing the original paint pattern to darken or even change color, which cannot meet current needs.

[0003] In summary, the development of an anti-permeability automotive paint protective film is of great significance in addressing the aforementioned issues. Summary of the Invention

[0004] The purpose of this invention is to provide an anti-penetration automotive paint protective film and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] An anti-permeability automotive paint protection film includes a transparent base film, and a first coating and a second coating sequentially disposed on its surface; the first coating is formed by an epoxy resin modified polyurethane coating, and the second coating is formed by a graphene modified polyurethane coating.

[0007] The epoxy resin modified polyurethane coating comprises the following raw materials, by weight: 40-50 parts polyisocyanate, 70-80 parts polyester polyol, 150 parts solvent, 4-8 parts 1,4-butanediol, 1-2 parts triethylene glycol, 0.05-0.1 parts dibutyltin dilaurate, 10-15 parts branched epoxy resin, and 5-7 parts polyfunctional polyetheramine.

[0008] Preferably, the preparation of the epoxy resin modified polyurethane coating includes the following steps: under a nitrogen atmosphere, polyisocyanate is added to polyester polyol and mixed evenly, and stirred at 60-70°C for 1-2 hours; solvent, 1,4-butanediol, triethylene glycol, and dibutyltin dilaurate are added sequentially, and stirred at 75-85°C for 1-1.5 hours; branched epoxy resin is added, and stirring is continued for 1-2 hours; multifunctional polyetheramine is added at 50-55°C, and mixed evenly to obtain the epoxy resin modified polyurethane coating.

[0009] A preferred method for preparing the branched epoxy resin is as follows: ethylene glycol diglycidyl ether and tetrabutylammonium bromide are mixed evenly and stirred at 125-130°C for 10-15 minutes under a nitrogen atmosphere. Neopentyl glycol diglycidyl ether is added, and trimethylolpropane and pentaerythritol allyl ether are mixed evenly and preheated to 100°C. The mixture is then gradually added dropwise to the reaction system, with the addition time controlled at 2 hours. The mixture is then stirred at 155-165°C for 6-8 hours to obtain the branched epoxy resin.

[0010] Preferably, the branched epoxy resin comprises the following raw materials, in parts by weight: 15-17 parts ethylene glycol diglycidyl ether, 1.5-1.7 parts tetrabutylammonium bromide, 2-2.2 parts neopentyl glycol diglycidyl ether, 4.6-4.8 parts trimethylolpropane, and 1.2-1.4 parts pentaerythritol allyl ether.

[0011] Preferably, the graphene-modified polyurethane coating comprises the following raw materials, in parts by weight: 30-40 parts polyester polyol, 30-50 parts polyether polyol, 40-50 parts polyisocyanate, 200 parts solvent, 10-12 parts 1,4-butanediol, 1-2 parts butene glycol, 0.05-0.1 parts dibutyltin dilaurate, 2-3 parts modified graphene oxide, 0.5-1 part leveling agent, and 0.01-0.03 parts azobisisobutyronitrile.

[0012] A preferred method for preparing the graphene-modified polyurethane coating is as follows: under a nitrogen atmosphere, polyester polyol and polyether polyol are mixed evenly, polyisocyanate is added, and the mixture is stirred at 60-70°C for 1-2 hours; solvent, 1,4-butanediol, butenediol, and dibutyltin dilaurate are added sequentially, and the mixture is stirred at 75-85°C for 1-1.5 hours; modified graphene oxide is added, and the mixture is stirred for another 1-2 hours; leveling agent and azobisisobutyronitrile are added, and the mixture is stirred evenly to obtain the graphene-modified polyurethane coating.

[0013] A preferred method for preparing the modified graphene oxide is as follows: graphene oxide is added to N,N-dimethylformamide and ultrasonically dispersed evenly; hyperbranched polyester, hydroxypropyl methacrylate, and tetrabutylammonium bromide are added; the mixture is heated and refluxed at 120-130°C for 20-24 hours; the mixture is then filtered, washed, and dried to obtain the modified graphene oxide.

[0014] The modified graphene oxide comprises the following raw materials, by weight: 0.4-0.6 parts graphene oxide, 50-60 parts N,N-dimethylformamide, 10-12 parts hyperbranched polyester, 2-3 parts hydroxypropyl methacrylate, and 0.02-0.03 parts tetrabutylammonium bromide.

[0015] Preferably, the molecular weight of the hyperbranched polyester is 1500-2000.

[0016] A preferred embodiment of the method for preparing an anti-penetration automotive paint protective film includes the following steps:

[0017] An epoxy resin-modified polyurethane coating is coated on one side of a transparent base film, and then cured by heating and annealing to form the first coating. A graphene-modified polyurethane coating is further coated on the same side, and then cured by heating, irradiated with ultraviolet light, and dried to form the second coating. This yields an anti-permeability automotive paint protection film.

[0018] Preferably, during the heat curing process, the temperature is 100~120℃ and the time is 4~6 min; during the annealing process, the temperature is 65~75℃ and the time is 1~1.5 h; during the secondary heat curing process, the temperature is 110~130℃ and the time is 2~5 min; during the ultraviolet irradiation process, the power is 600~800W and the time is 5~10 min, repeated three times with an interval of 4~5 min between each time.

[0019] The thickness of the first coating is 100~150μm; the thickness of the second coating is 15~30μm.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention forms a protective layer structure with a flexible bottom and a rigid top by preparing a high-strength and high-toughness anti-permeability first coating with branched epoxy resin modified polyurethane coating and a wear-resistant and anti-permeability second coating with graphene modified polyurethane coating. This improves the anti-permeability and protective effect of the car paint protective film without significantly reducing the light transmittance.

[0021] The branched epoxy resin is prepared by using trimethylolpropane and pentaerythritol allyl ether as branching monomers and ethylene glycol diglycidyl ether and neopentyl glycol diglycidyl ether as linear monomers. This invention improves the crosslinking density by preparing branched epoxy resin modified polyurethane coatings, and the prepared branched epoxy resin has a lower viscosity, which is beneficial for dispersion in polyurethane coatings, thereby increasing the strength and anti-leakage performance of the protective film.

[0022] In this process, graphene is synergistically modified with hyperbranched polyester and hydroxypropyl methacrylate. On one hand, this improves the dispersibility of graphene in the polyurethane coating, enhancing the wear resistance and impermeability of the protective film. On the other hand, the multi-oxygen groups of the hyperbranched polyester can intercalate between the graphene layers, resulting in exfoliated monolayer graphene sheets, reducing the impact on light transmittance and increasing transparency. However, the molecular weight of the hyperbranched polyester should not be too large, as this can easily lead to agglomeration, weakening the graphene intercalation modification and reducing film uniformity, thus decreasing wear resistance and light transmittance. Furthermore, the graphene-modified polyurethane coating should not be too thick, as this will reduce transparency; a thickness of 15–30 μm is ideal.

[0023] This invention involves multiple interval UV treatments after heat curing, which helps to uniformly crosslink the double bonds in the protective film and further improves the anti-permeability performance. At the same time, graphene oxide is also reduced to graphene, which increases the tightness of the bond with the matrix, thereby improving the protective performance while reducing the impact on light transmittance. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the following quantities are by weight. There are no special restrictions on the manufacturers from which the raw materials involved in this invention were purchased. Exemplary examples include: ethylene glycol diglycidyl ether (CAS No.: 2224-15-9); neopentyl glycol diglycidyl ether (CAS No.: 17557-23-2); trimethylolpropane (CAS No.: 77-99-6); pentaerythritol allyl ether (CAS No.: 91648-24-7); 1,4-butanediol (CAS No.: 110-63-4); triethylene glycol (CAS No.: 112-27-6); graphene oxide with a particle size of 50-100 nm; hyperbranched polyester, model Boltorn H30, provided by Shanghai Xibao Biotechnology Co., Ltd.; hydroxypropyl methacrylate (CAS No.: 27813-02-1); butene glycol (CAS No.: 497-06-3). In the following examples, all the above-mentioned and other raw materials used but not mentioned were commercially available.

[0026] In the embodiments and comparative examples, the polyisocyanate is isophorone diisocyanate; the polyester polyol is Dynacoll 7150; the polyether polyol is PTMEG-1000; the solvent is a mixture of toluene and N,N-dimethylformamide in a volume ratio of 1:1; the transparent base film is a PET film; and the leveling agent is BYK-333.

[0027] Example 1: A method for preparing an anti-permeability automotive paint protective film, comprising the following steps:

[0028] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0029] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 45 parts of polyisocyanate were added to 75 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 6 parts of 1,4-butanediol, 1.5 parts of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 12 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 6 parts of polyfunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0030] Step 3: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. 11 parts of hyperbranched polyester, 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0031] Step 4: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 35 parts of polyester polyol and 40 parts of polyether polyol were mixed evenly, and 45 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 11 parts of 1,4-butanediol, 1.5 parts of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 2.5 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0032] Step 5: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0033] Example 2: A method for preparing an anti-permeability automotive paint protective film, comprising the following steps:

[0034] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0035] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 40 parts of polyisocyanate were added to 70 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 4 parts of 1,4-butanediol, 1 part of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 10 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 5 parts of multifunctional polyetheramine were added at 50°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0036] Step 3: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. 11 parts of hyperbranched polyester, 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0037] Step 4: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 30 parts of polyester polyol and 30 parts of polyether polyol were mixed evenly, and 40 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 10 parts of 1,4-butanediol, 1 part of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 2 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0038] Step 5: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0039] Example 3: A method for preparing an anti-permeability automotive paint protective film, comprising the following steps:

[0040] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0041] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 50 parts of polyisocyanate were added to 80 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 8 parts of 1,4-butanediol, 2 parts of triethylene glycol, and 0.1 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 15 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 7 parts of multifunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0042] Step 3: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. 11 parts of hyperbranched polyester, 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0043] Step 4: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 40 parts of polyester polyol and 50 parts of polyether polyol were mixed evenly, and 50 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 12 parts of 1,4-butanediol, 2 parts of butene diol, and 0.1 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 3 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 1 part of leveling agent and 0.03 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0044] Step 5: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0045] Comparative Example 1: Based on Example 1, in the preparation of epoxy resin modified polyurethane coating, commercially available E51 epoxy resin was used instead, while the rest of the process remained unchanged, as follows:

[0046] Step 1: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 45 parts of polyisocyanate were added to 75 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 6 parts of 1,4-butanediol, 1.5 parts of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 12 parts of E51 epoxy resin were added, and stirring was continued for 1.5 h; 6 parts of multifunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0047] Step 2: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. Then, 11 parts of hyperbranched polyester, 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0048] Step 3: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 35 parts of polyester polyol and 40 parts of polyether polyol were mixed evenly, and 45 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 11 parts of 1,4-butanediol, 1.5 parts of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 2.5 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0049] Step 4: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0050] Comparative Example 2: Based on Example 1, during the preparation of modified graphene, the molecular weight of the hyperbranched polyester was increased to 4000, while the rest of the process remained unchanged, as follows:

[0051] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0052] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 45 parts of polyisocyanate were added to 75 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 6 parts of 1,4-butanediol, 1.5 parts of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 12 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 6 parts of polyfunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0053] Step 3: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. Then, 11 parts of hyperbranched polyester (molecular weight 4000), 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0054] Step 4: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 35 parts of polyester polyol and 40 parts of polyether polyol were mixed evenly, and 45 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 11 parts of 1,4-butanediol, 1.5 parts of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 2.5 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0055] Step 5: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0056] Comparative Example 3: Based on Example 1, without ultraviolet light treatment, the remaining processes remain unchanged, as follows:

[0057] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0058] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 45 parts of polyisocyanate were added to 75 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 6 parts of 1,4-butanediol, 1.5 parts of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 12 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 6 parts of polyfunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0059] Step 3: Preparation of modified graphene: 0.5 parts of graphene oxide were added to 55 parts of N,N-dimethylformamide and ultrasonically dispersed evenly. 11 parts of hyperbranched polyester, 2.5 parts of hydroxypropyl methacrylate, and 0.02 parts of tetrabutylammonium bromide were added. The mixture was heated and stirred under reflux at 125°C for 24 hours. After filtration, washing, and drying, modified graphene oxide was obtained.

[0060] Step 4: Preparation of graphene-modified polyurethane coating: Under a nitrogen atmosphere, 35 parts of polyester polyol and 40 parts of polyether polyol were mixed evenly, and 45 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 11 parts of 1,4-butanediol, 1.5 parts of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h. Then, 2.5 parts of modified graphene oxide were added, and the mixture was stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added, and the mixture was stirred evenly to obtain the graphene-modified polyurethane coating.

[0061] Step 5: Preparation of anti-permeability automotive paint protection film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, and anneal at 70℃ for 1 hour to form the first coating; further apply graphene modified polyurethane coating to this side, heat and cure at 120℃ for 3 minutes, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protection film.

[0062] Comparative Example 4: Based on Example 1, without adding modified graphene, and with the other processes remaining unchanged, as follows:

[0063] Step 1: Preparation of branched epoxy resin; Mix 16 parts of ethylene glycol diglycidyl ether and 1.6 parts of tetrabutylammonium bromide evenly, stir at 125°C for 15 min under nitrogen atmosphere, add 2.1 parts of neopentyl glycol diglycidyl ether, and mix 4.7 parts of trimethylolpropane and 1.3 parts of pentaerythritol allyl ether evenly. After preheating to 100°C, gradually add the mixture dropwise to the reaction system, controlling the dropwise addition time to 2 h. Continue stirring at 160°C for 6 h to obtain branched epoxy resin;

[0064] Step 2: Preparation of epoxy resin modified polyurethane coating: Under a nitrogen atmosphere, 45 parts of polyisocyanate were added to 75 parts of polyester polyol and mixed evenly, and stirred at 65°C for 1.5 h; 150 parts of solvent, 6 parts of 1,4-butanediol, 1.5 parts of triethylene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially, and stirred at 80°C for 1 h; 12 parts of branched epoxy resin were added, and stirring was continued for 1.5 h; 6 parts of polyfunctional polyetheramine were added at 55°C and mixed evenly to obtain epoxy resin modified polyurethane coating;

[0065] Step 3: Preparation of modified polyurethane coating A: Under a nitrogen atmosphere, 35 parts of polyester polyol and 40 parts of polyether polyol were mixed evenly, and 45 parts of polyisocyanate were added. The mixture was stirred at 65°C for 1.5 h. Then, 200 parts of solvent, 11 parts of 1,4-butanediol, 1.5 parts of butene glycol, and 0.05 parts of dibutyltin dilaurate were added sequentially. The mixture was stirred at 80°C for 1 h and then stirred for another 1.5 h. Finally, 0.5 parts of leveling agent and 0.01 parts of azobisisobutyronitrile were added and stirred evenly to obtain modified polyurethane coating A.

[0066] Step 4: Preparation of anti-permeability automotive paint protective film: Apply epoxy resin modified polyurethane coating to one side of the transparent base film, heat and cure at 110℃ for 5 minutes, anneal at 70℃ for 1 hour to form the first coating; further apply modified polyurethane coating A to this side, heat and cure at 120℃ for 3 minutes, treat with 600W ultraviolet light for 8 minutes, repeat three times with a 5-minute interval between each treatment, and dry to form the second coating; thus obtaining the anti-permeability automotive paint protective film.

[0067] Performance testing: The samples prepared in each embodiment were subjected to the following tests in sequence: (1) The transmittance of each embodiment and comparative sample was tested according to GB / T2410-2008; (2) Each embodiment and comparative sample was attached to the car paint panel, and the protective film was repeatedly scraped 10 times with a copper brush. The surface condition of the protective film was observed; (3) The tensile strength of each embodiment and comparative sample was measured according to GB1040-79; (4) Each embodiment and comparative sample was attached to the car paint panel, and a drop of Biaobang brand carburetor cleaner (B-1091) was added. The sample was left to stand for 5 minutes and the sample was observed to see if it was damaged in order to test its impermeability; The experimental data are shown in Table 1.

[0068] Table 1

[0069]

[0070] Conclusion: As shown in Table 1, the present invention has excellent light transmittance, abrasion resistance and tensile strength, and the cleaning agent does not cause damage after treatment, demonstrating excellent anti-permeability. In addition, since no graphene oxide was added in Comparative Example 4, the light transmittance of Example 1 did not decrease significantly. This indicates that the protective film prepared by the present invention can maintain light transmittance while having excellent abrasion resistance, tensile strength and anti-permeability, thus providing excellent protective effect.

[0071] Comparative Example 1 used commercially available E51 epoxy resin, which resulted in a decrease in crosslinking density and tensile strength. Comparative Example 2 increased the molecular weight of the hyperbranched polyester, leading to agglomeration and a decrease in light transmittance. Comparative Example 3 did not undergo UV irradiation treatment, resulting in a lack of UV initiation, a decrease in crosslinking density, and the graphene oxide was not reduced, leading to a decrease in rigidity. Comparative Example 4 did not add modified graphene, resulting in a decrease in wear resistance and impermeability.

[0072] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an anti-permeability automotive paint protective film, characterized in that: Includes the following steps: An epoxy resin-modified polyurethane coating is applied to one side of a transparent base film, and then cured and annealed in one step to form the first coating. The surface is further coated with a graphene-modified polyurethane coating, cured by secondary heating, and then dried under ultraviolet light to form a second coating. Obtain an anti-penetration protective film for automotive paint; The epoxy resin modified polyurethane coating comprises the following raw materials, by weight: 40-50 parts polyisocyanate, 70-80 parts polyester polyol, 150 parts solvent, 4-8 parts 1,4-butanediol, 1-2 parts triethylene glycol, 0.05-0.1 parts dibutyltin dilaurate, 10-15 parts branched epoxy resin, and 5-7 parts polyfunctional polyetheramine; The graphene-modified polyurethane coating comprises the following raw materials, by weight: 30-40 parts polyester polyol, 30-50 parts polyether polyol, 40-50 parts polyisocyanate, 200 parts solvent, 10-12 parts 1,4-butanediol, 1-2 parts butene glycol, 0.05-0.1 parts dibutyltin dilaurate, 2-3 parts modified graphene oxide, 0.5-1 part leveling agent, and 0.01-0.03 parts azobisisobutyronitrile; The modified graphene oxide is prepared by: adding graphene oxide into N,N-dimethylformamide and dispersing it evenly by ultrasonication; adding hyperbranched polyester, hydroxypropyl methacrylate, and tetrabutylammonium bromide; heating and refluxing at 120~130℃ for 20~24h; filtering, washing, and drying to obtain modified graphene oxide. The modified graphene oxide comprises the following raw materials, in parts by weight: 0.4-0.6 parts graphene oxide, 50-60 parts N,N-dimethylformamide, 10-12 parts hyperbranched polyester, 2-3 parts hydroxypropyl methacrylate, and 0.02-0.03 parts tetrabutylammonium bromide. The hyperbranched polyester has a molecular weight of 1500-2000.

2. The method for preparing an anti-permeability automotive paint protective film according to claim 1, characterized in that: The preparation of the epoxy resin modified polyurethane coating includes the following steps: under a nitrogen atmosphere, polyisocyanate is added to polyester polyol and mixed evenly, and stirred at 60~70℃ for 1~2h; solvent, 1,4-butanediol, triethylene glycol, and dibutyltin dilaurate are added sequentially, and stirred at 75~85℃ for 1~1.5h; branched epoxy resin is added, and stirring is continued for 1~2h; multifunctional polyetheramine is added at 50~55℃, and mixed evenly to obtain the epoxy resin modified polyurethane coating.

3. The method for preparing an anti-permeability automotive paint protective film according to claim 1, characterized in that: The preparation method of the branched epoxy resin is as follows: Ethylene glycol diglycidyl ether and tetrabutylammonium bromide are mixed evenly and stirred at 125~130℃ for 10~15 min under a nitrogen atmosphere. Neopentyl glycol diglycidyl ether is added, and trimethylolpropane and pentaerythritol allyl ether are mixed evenly and preheated to 100℃. The mixture is then gradually added dropwise to the reaction system, and the dropwise addition time is controlled to be 2 h. The mixture is stirred at 155~165℃ for 6~8 h to obtain the branched epoxy resin.

4. The method for preparing an anti-penetration automotive paint protective film according to claim 3, characterized in that: The branched epoxy resin comprises the following raw materials, in parts by weight: 15-17 parts ethylene glycol diglycidyl ether, 1.5-1.7 parts tetrabutylammonium bromide, 2-2.2 parts neopentyl glycol diglycidyl ether, 4.6-4.8 parts trimethylolpropane, and 1.2-1.4 parts pentaerythritol allyl ether.

5. The method for preparing an anti-permeability automotive paint protective film according to claim 1, characterized in that: The preparation method of the graphene-modified polyurethane coating is as follows: under a nitrogen atmosphere, polyester polyol and polyether polyol are mixed evenly, polyisocyanate is added, and the mixture is stirred at 60~70℃ for 1~2h; solvent, 1,4-butanediol, butenediol, and dibutyltin dilaurate are added sequentially, and the mixture is stirred at 75~85℃ for 1~1.5h; modified graphene oxide is added, and the mixture is stirred for another 1~2h; leveling agent and azobisisobutyronitrile are added, and the mixture is stirred evenly to obtain the graphene-modified polyurethane coating.

6. The method for preparing an anti-permeability automotive paint protective film according to claim 1, characterized in that: During the heating and curing process, the temperature is 100~120℃ and the time is 4~6 minutes; during the annealing process, the temperature is 65~75℃ and the time is 1~1.5 hours; during the secondary heating and curing process, the temperature is 110~130℃ and the time is 2~5 minutes; during the ultraviolet irradiation process, the power is 600~800W and the time is 5~10 minutes, repeated three times with an interval of 4~5 minutes between each time. The thickness of the first coating is 100~150μm; The thickness of the second coating is 15~30μm.

7. The anti-permeability automotive paint protective film prepared by the method of preparing an anti-permeability automotive paint protective film according to any one of claims 1 to 6.

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