A tpu-based primer composition for a paint protection film and its coating method and use

Abstract

The application belongs to the technical field of automobile paint protection film, and particularly relates to a TPU base film interface anti-migration primer composition for a paint protection film and a coating method and application thereof. The primer composition comprises, by mass fraction, 30-50 parts of an aliphatic water-based polyurethane dispersion, 2-5 parts of an amino silane coupling agent, 3-8 parts of a multifunctional aliphatic isocyanate crosslinking agent, 1-10 parts of inorganic filler dispersion slurry, 10-25 parts of an organic solvent, 30-50 parts of deionized water and an appropriate amount of an auxiliary agent. The primer composition of the application is integrated in the existing PPF production line through an online micro-concave coating method. After the primer layer is applied, the TPU base film has a decreased haze value, a decreased defect rate of repairing coating leakage, an improved interlayer peeling strength, a decreased adhesion force attenuation rate after heat aging, and excellent comprehensive performance.

Description

Technical Field

[0001] This invention belongs to the field of automotive paint protection film technology, specifically relating to a TPU base film interface anti-migration primer composition for paint protection film, its coating method and application. Background Technology

[0002] Paint protection film (PPF) is a transparent polymer film applied to the surface of a car's paintwork to protect the original paint from external damage such as stone impacts, scratches, UV radiation, acid rain corrosion, and chemical pollution. In recent years, paint protection films based on thermoplastic polyurethane elastomer (TPU) have gradually replaced earlier PVC and TPH substrates and become the mainstream choice in the high-end paint protection film market due to their excellent tensile strength, elongation at break, abrasion resistance, weather resistance, and self-healing capabilities.

[0003] In the extrusion casting process of TPU base film, various low molecular weight additives are typically added to improve processing performance, weather resistance, and surface smoothness. These additives include antioxidants, UV absorbers, smoothing agents, and processing aids (such as zinc stearate and calcium stearate). The molecular weights of these additives are generally in the range of 300-800 g / mol, and their compatibility with the TPU polymer matrix is ​​limited. These low molecular weight components continuously migrate and precipitate onto the surface during storage and use, forming a so-called "weak boundary layer" on the TPU surface. The negative impact of additive migration and precipitation on the protective coating product is mainly reflected in two aspects: First, when precipitated additives are present on the TPU surface, the interfacial adhesion between the base coat and the TPU surface decreases sharply during the subsequent application of the self-healing coating. This results in the coating liquid failing to spread evenly on the TPU surface, leading to localized missed coatings (i.e., pinhole defects), severely affecting the product's appearance quality and protective performance. Secondly, when the interface between the pressure-sensitive adhesive layer and the TPU is contaminated by migrating additives, a weak interface layer forms at the bonding interface, leading to adhesion failure. This results in serious quality problems such as reduced adhesion, delamination, and even complete peeling of the entire layer during long-term use. The industry standard TCSTM01150-2024, "Aliphatic Thermoplastic Polyurethane (TPU) Granules for Paint Protective Films," lists "blooming resistance" as one of the key performance indicators for TPU films in section 5.2.7 and Appendix A, requiring that the haze increase after accelerated aging at 80℃ / 24h does not exceed 2.0%, and that no visible blemishes are present.

[0004] Currently, the industry primarily uses surface activation methods such as corona treatment or plasma treatment to address the issue of additive precipitation on TPU film surfaces. However, extensive technical literature and engineering practice show that the corona treatment effect fades much faster for films containing additives than for films without additives. The fundamental reason is that low molecular weight additives continuously precipitate and coat the film surface, counteracting the polar groups introduced by the corona treatment. More importantly, the effect of corona treatment is significantly time-sensitive—the longer the storage time, the more additives precipitate, and the more severe the decay of the corona activation effect. For downstream coating companies that purchase TPU films from base film suppliers, the storage period of the base film and the state of additive precipitation are completely uncontrollable. This is the root cause of problems such as "easy leakage of repair adhesive" and "later viscosity reduction" in production. Furthermore, surface activation methods such as corona treatment and plasma treatment do not address the impact of the compatibility between the primer and TPU on additive migration. Those skilled in the art often consider the compatibility between PUD and TPU to be a favorable factor and tend to choose primer materials with similar chemical structures, failing to realize that this also creates conditions for additive migration. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a TPU base film interface anti-migration primer composition for paint protection films. This composition maintains high compatibility with the TPU base film while achieving efficient barrier properties, blocking the migration channels of internal TPU additives at the source. It also ensures long-term stable adhesion of the upper coating layer and the lower adhesive layer, possessing significant engineering value and broad commercial prospects.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a TPU base film interface anti-migration primer composition for paint protection film, comprising the following components by weight: 30-50 parts of aliphatic waterborne polyurethane dispersion; 2-5 parts of aminosilane coupling agent; 3-8 parts of multifunctional aliphatic isocyanate crosslinking agent; 1-10 parts of inorganic filler dispersion slurry; 10-25 parts of organic solvent; and 30-50 parts of deionized water, wherein the inorganic filler content in the inorganic filler dispersion slurry is 19-50 wt%, and the inorganic filler accounts for 0.2%-5% of the total mass of the composition.

[0007] Preferably, the composition further includes adjuvants.

[0008] Preferably, the additives include at least one or more of leveling agents, defoamers, and wetting agents.

[0009] A TPU base film interface anti-migration primer composition for paint protection film, comprising the following components by weight: 30-50 parts aliphatic waterborne polyurethane dispersion; 2-5 parts aminosilane coupling agent; 3-8 parts multifunctional aliphatic isocyanate crosslinking agent; 1-10 parts inorganic filler dispersion slurry; 10-25 parts organic solvent; 30-50 parts deionized water; 0.3-0.8 parts leveling agent; 0.1-0.3 parts defoamer; and 0.1-0.3 parts wetting agent.

[0010] Preferably, the aliphatic waterborne polyurethane dispersion has a solid content of 35% to 45%, a glass transition temperature (Tg) of -20°C to 10°C, and a number-average molecular weight (Mn) of 20,000 to 60,000 g / mol.

[0011] This invention selects an aliphatic aqueous polyurethane dispersion with a glass transition temperature (Tg) of -20℃ to 10℃, which exhibits good film-forming properties at room temperature and also shows segment miscibility with the soft segments of the TPU base film. Furthermore, the molecular weight of the aliphatic aqueous polyurethane dispersion ensures a balance between film strength and segment migration; if the molecular weight is too low, the film strength is insufficient, while if the molecular weight is too high, the segment miscibility with TPU decreases.

[0012] Preferably, the molecular chain of the aliphatic waterborne polyurethane dispersion contains both urethane bonds (-NH-COO-) and urea groups (-NH-CO-NH-).

[0013] Aliphatic waterborne polyurethane dispersions contain the aforementioned groups, which can improve the chemical compatibility between the primer composition and the TPU base film, enabling the formation of molecular-level interfacial miscibility and entanglement.

[0014] Preferably, the aliphatic aqueous polyurethane dispersion is prepared by reacting an aliphatic diisocyanate with polycaprolactone polyol and / or polycarbonate polyol.

[0015] Preferably, the aliphatic diisocyanate is selected from at least one of HDI and IPDI. Preferably, the aminosilane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane (KH-550), γ-aminopropyltrimethoxysilane (KH-540), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (KH-792), or N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane (DL-602).

[0016] This invention incorporates an aminosilane coupling agent into the primer composition. Compared to other types of silane coupling agents such as epoxy silanes, the aminosilane coupling agent used in this invention has higher reactivity of its amino groups with the isocyanate groups on the TPU surface, and can form stable urea bonds at lower temperatures. The amino groups also participate in the isocyanate crosslinking reaction, acting as nodes in the crosslinking network to achieve the coupling of chemical anchoring and physical barrier. The silanol groups generated from the hydrolysis of aminosilane react with the multifunctional aliphatic isocyanate crosslinking agent to form an organic-inorganic hybrid network, which improves anti-exudation and light transmittance.

[0017] Preferably, the multifunctional aliphatic isocyanate crosslinking agent is selected from one or more of hexamethylene diisocyanate (HDI) trimer, HDI biuret polyisocyanate, isophorone diisocyanate (IPDI) trimer, or HDI / IPDI mixed trimer.

[0018] The crosslinking agent selected in this invention contains ≥ three isocyanate groups (-NCO) in its molecular structure. This allows it to crosslink with the hydroxyl and amino groups on the molecular chains of aliphatic waterborne polyurethane dispersions, as well as the silanol groups generated after the hydrolysis of aminosilane coupling agents, forming a highly dense three-dimensional network structure and improving resistance to exudation. Compared to difunctional isocyanates, the trifunctional and higher-functionality crosslinking agent selected in this invention can form a true three-dimensional crosslinked network without linear chain growth, resulting in better barrier effects against the migration of internal TPU additives to the surface.

[0019] Preferably, the nano-inorganic filler is selected from one or more of fumed silica, cage-like polysilsesquioxane, or surface-modified layered silicates. Preferably, the fumed silica has a particle size of 10-50 nm and a specific surface area of ​​100-400 m² / g.

[0020] Preferably, the particle size of the cage-shaped polysilsesquioxane (POSS) is 1~3nm.

[0021] Preferably, the cage-like polysilsesquioxane comprises one or more of octaaminoPOSS, octaepoxyPOSS, or octavinylPOSS.

[0022] More preferably, the cage-like polysilsesquioxane is octaaminoPOSS.

[0023] The surface-modified nanolayered silicate is an organo-modified montmorillonite with a layer thickness of 1-2 nm and a layer diameter of 100-500 nm.

[0024] Commonly used inorganic fillers in existing coatings include calcium carbonate, titanium dioxide, talc, kaolin, barium sulfate, and carbon black. However, the inorganic fillers used in the primer composition of this invention are not chosen arbitrarily. The inorganic fillers used in this invention cannot be merely physical fillers. The silanol groups on the surface of the selected vapor-phase nano-SiO2 can participate in the hydrolysis and condensation network of the silane coupling agent; the active groups (amino / epoxy / vinyl) at the POSS vertices can covalently bond with the isocyanate crosslinking agent to form star-shaped crosslinking nodes; and the lamellar layers of organo-modified montmorillonite can be oriented and arranged in the coating to form barriers. This satisfies the requirements of nanoscale size, high transparency, low light scattering, and chemical bonding ability with the crosslinking network or oriented barrier structure, thus forming a better synergistic effect with other components in the primer composition.

[0025] Preferably, the organic solvent is selected from one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, isopropanol, n-butanol, or ethanol.

[0026] The role of organic solvents is to adjust the viscosity and drying rate of the primer composition, ensuring that the primer composition has good leveling and transfer efficiency during the microgravure coating process. The solvents of this invention have higher compatibility with PUD dispersions, better dispersion ability for nanofillers, and better matching with upstream and downstream coating processes.

[0027] Preferably, the leveling agent is selected from at least one of polyether-modified polysiloxane leveling agents or acrylate leveling agents.

[0028] Preferably, the defoamer is selected from at least one of polysiloxane defoamers or mineral oil defoamers.

[0029] Preferably, the wetting agent is selected from at least one of nonionic fluorocarbon surfactants or polyether-modified silicone wetting agents.

[0030] Preferably, the preparation method of the TPU base film interface anti-migration primer composition for paint protection film includes the following steps: mixing and stirring aliphatic waterborne polyurethane dispersion, aminosilane coupling agent, organic solvent and deionized water according to the formula ratio; then adding inorganic filler dispersion slurry and stirring at high speed; then adding multifunctional aliphatic isocyanate crosslinking agent, leveling agent, defoamer and wetting agent, stirring evenly and filtering to obtain the TPU base film interface anti-migration primer composition for paint protection film.

[0031] The coating method for the TPU base film interface anti-migration primer composition used for paint protection film includes the following steps: (1) A primer coating station is added between the TPU unwinding device and the functional coating section. The primer coating station includes a gravure coating system and a short oven. (2) The primer composition is uniformly coated onto the surface of the TPU base film using a microgravure coating system to form a primer coating layer; (3) The TPU base film after the primer composition is coated is dried and cured to obtain the TPU base film after primer treatment.

[0032] The TPU base film includes any one of aliphatic polycaprolactone type, polycarbonate type, polyether type, or copolymer type TPU film.

[0033] The application of the TPU base film interface anti-migration primer composition for paint protection film, wherein the anti-migration primer composition is used to prepare paint protection film, and the preparation method includes the following steps: (1) A primer coating station is added between the TPU unwinding device and the functional coating section. The primer coating station includes a gravure coating system and a short oven. (2) The primer composition is uniformly coated onto the surface of the TPU base film using a microgravure coating system to form a primer coating layer; (3) The TPU base film after coating with the primer composition is dried and cured to obtain the TPU base film after primer treatment; (4) The TPU base film after the primer treatment directly enters the functional coating section. A self-healing thermosetting polyurethane coating liquid is applied to the surface of the primer, and then it enters the main oven for full drying and cross-linking curing. Subsequently, the composite with PET protective film, pressure-sensitive adhesive coating, composite with release film, and curing are completed in sequence according to conventional processes to obtain a paint surface protective film with an anti-migration primer.

[0034] Preferably, the primer coating station includes a microgravure coating system (including microgravure rollers, doctor blades, adhesive trays, and back pressure rollers) and a short drying oven (3-6 meters in length, with zoned temperature control). The configuration of the microgravure coating system is compatible with existing functional coating microgravure coating sections, eliminating the need for large-scale modifications to the main production line.

[0035] Preferably, for applications requiring improved interfacial performance of the pressure-sensitive adhesive layer, the same primer composition can be applied to the other side (mounting surface) of the TPU base film before applying the pressure-sensitive adhesive layer. This double-sided primer application simultaneously addresses both issues of missed coating in the repair layer and reduced adhesion of the mounting layer, making it particularly suitable for high-end car cover products and applications in harsh environments (such as high-temperature and high-humidity areas).

[0036] Preferably, the solid content of the primer composition is controlled at 15% to 25%, the viscosity is controlled at 50 to 200 mPa·s (25°C, Brookfield viscometer), and the surface tension is controlled at 25 to 35 mN / m.

[0037] Preferably, the TPU base film is drawn out from the unwinding device and passes through the micro-grooving base coating station at a linear speed of 5~20m / min. The cell volume of the micro-grooving roller is controlled at 20~80μm³ / cm², the doctor blade pressure is controlled at 0.1~0.3MPa, and the back pressure roller pressure is controlled at 0.2~0.5MPa.

[0038] Preferably, the short drying oven employs a three-stage temperature control: the first stage temperature is 50~70℃, with a drying time of 10~20 seconds; the second stage temperature is 70~90℃, with a drying time of 20~40 seconds; and the third stage temperature is 90~110℃, with a drying time of 40~60 seconds. The total drying time in the short drying oven is 70~120 seconds, ensuring that the base coating reaches a surface-dry state (touch-dry), and the dry film thickness is controlled within 0.5~2.0μm.

[0039] The three-stage temperature control used in this invention precisely matches the temperature setting with the chemical reaction mechanism of each component. The three-stage temperature control ensures a better synergistic effect between the chemical anchoring and physical barrier of the primer composition, and improves the coating omission caused by unstable surface drying degree.

[0040] Preferably, the primer composition may be located between the base film and the coating layer, or between the base film and the pressure-sensitive adhesive layer.

[0041] In one embodiment, the paint protection film sequentially comprises a PET release film, a pressure-sensitive adhesive layer, a TPU base film, a primer composition, a self-healing polyurethane coating, and a PET protective film.

[0042] In one embodiment, the paint protection film sequentially comprises a PET release film, a pressure-sensitive adhesive layer, a primer composition, a TPU base film, a self-healing polyurethane coating, and a PET protective film.

[0043] Preferably, the protective coating film has an anti-exudation ΔH of 0.3%~0.8%; an interlayer peel strength of 9.5N / 25mm~14.8N / 25mm; a pressure-sensitive adhesive peel strength of 11.5N / 25mm~17.5N / 25mm; an tack decay rate of 6.1%~12.2%; a missing coating defect rate of 0.03%~0.15%; and a light transmittance of 90.8%~92.5%.

[0044] The beneficial effects of this invention are as follows: (1) The primer composition provided by the present invention can block the migration channel of low molecular weight additives from the source and inhibit the formation of weak boundary layer through the synergistic effect of multiple components. The paint protection film prepared by the primer composition of the present invention has excellent performance in terms of anti-precipitation, interfacial adhesion, long-term aging resistance, coating yield and optical transparency. It solves the problems in the prior art that TPU base film continuously migrates to the surface and precipitates due to the addition of low molecular weight additives during storage and use, forming a weak boundary layer, which leads to the problem of missed coating of self-healing functional coating and delamination of pressure sensitive adhesive layer. (2) The primer composition and coating method of the present invention can be integrated online with the existing PPF production line and is compatible with the micro-recessed coating section of the functional coating, without the need for large-scale modification of the main body of the production line; the surface energy of the base film will no longer continuously decrease with the extension of storage time, and it can still be directly coated after long-term storage without the need for re-corona treatment or secondary activation, thereby reducing inventory turnover pressure and batch quality risk; at the same time, double-sided primer coating can be applied to the mounting surface to simultaneously improve the problem of missed coating of the repair coating and the problem of reduced adhesion of the pressure-sensitive adhesive layer. Attached Figure Description

[0045] Figure 1 A schematic diagram illustrating the dual-function mechanism of chemical anchoring and physical barrier of the TPU base film interface anti-migration undercoating. Figure 2 This is a schematic diagram showing the integration of the online primer coating station in the paint protective film coating production line. Figure 3 A schematic diagram of interfacial failure of a TPU base film without an undercoat after additive migration; Figure 4 A schematic diagram of the interface structure of the TPU base film after applying the base coating of the present invention; Figure 5 SEM cross-sectional image of the paint protective film prepared in Example 1; Figure 6 SEM cross-sectional image of the interface transition region of the protective film for paint prepared in Example 1; Figure 7 TEM cross-sectional view of the paint protective film prepared in Example 1; Figure 8 TEM image of the interfacial bonding state of the protective film prepared in Example 1; Figure 9 SEM cross-sectional view of the interface transition region of the protective film prepared in Comparative Example 1; left side magnified 5000 times, middle side magnified 20000 times, right side magnified 50000 times. Figure 10 SEM cross-sectional view of the interface transition region of the protective film prepared in Comparative Example 2; left side magnified 5000 times, middle side magnified 20000 times, right side magnified 50000 times; Figure 11SEM cross-sectional view of the interface transition region of the protective film prepared in Comparative Example 3; left side magnified 5000 times, middle side magnified 20000 times, right side magnified 50000 times; Figure 12 The image shows a cross-sectional SEM image of the interface transition region of the protective film prepared in Comparative Example 4; the left side is magnified 5000 times, the middle side is magnified 20000 times, and the right side is magnified 50000 times. Figure 13 The image shows a cross-sectional SEM image of the interface transition zone of the protective film prepared in Comparative Example 5; the left side is magnified 5000 times, the middle side is magnified 20000 times, and the right side is magnified 50000 times. Detailed Implementation

[0046] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0047] Unless otherwise specified, all components used in this invention can be obtained by those skilled in the art through conventional purchase.

[0048] Aliphatic waterborne polyurethane dispersion PUD-A, solid content 40%, Tg=-5℃, is prepared based on HDI and polycaprolactone polyol, Wanhua Chemical, brand name Adwel®1645, molecular weight 150000~180000 g / mol.

[0049] Aliphatic waterborne polyurethane dispersion PUD-B, solid content 38%, Tg=0℃, based on IPDI and polycarbonate polyol, Covestro, brand name Bayhydrol® UH2895, molecular weight 100,000~150,000 g / mol.

[0050] Aliphatic waterborne polyurethane dispersion PUD-C, solid content 42%, Tg=5℃, based on HDI / IPDI mixed diisocyanate and polycaprolactone / polycarbonate copolyol, Oubaodi, brand name ALBERDINGK®U6150, molecular weight 80000~120000 g / mol.

[0051] Aliphatic waterborne polyurethane dispersion PUD-D, solid content 40%, Tg=30℃, Lubrizol, brand name SANCURE®843, molecular weight 50000~80000 g / mol.

[0052] Aliphatic waterborne polyurethane dispersion PUD-E, with a solid content of 40% and a Tg of -5℃, was prepared based on HDI and polyether polyol PTMG1000, with a number average molecular weight Mn of 35000 g / mol.

[0053] Aliphatic waterborne polyurethane dispersion PUD-H, with a solid content of 40% and a Tg of -5℃, is based on HDI and polycaprolactone polyol, with a number average molecular weight Mn of 10000 g / mol.

[0054] Aliphatic waterborne polyurethane dispersion PUD-I, with a solid content of 40% and a Tg of -5℃, is based on HDI and polycaprolactone polyol, with a number average molecular weight Mn of 15000 g / mol.

[0055] Aliphatic waterborne polyurethane dispersion PUD-J, solid content 40%, T g =-5℃, based on HDI and polycaprolactone polyol, number average molecular weight M n It is 80000 g / mol.

[0056] Aliphatic waterborne polyurethane dispersion PUD-K, solids content 40%, T g =-5℃, based on HDI and polycaprolactone polyol, number average molecular weight M n It is 100,000 g / mol.

[0057] KH-550, γ-aminopropyltriethoxysilane, purity ≥98%, Nanjing Shuguang.

[0058] KH-540, γ-aminopropyltrimethoxysilane, Nanjing Shuguang.

[0059] KH-792, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, Nanjing Shuguang.

[0060] DL-602, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, Nanjing Shuguang.

[0061] GPTMS, γ-glycidoxypropyltrimethoxysilane, Nanjing Shuguang.

[0062] HDI trimer, NCO content 21.5~22.5%, Covestro / Vencorex, brand name Desmodur N3300.

[0063] HDI dimer, NCO content 15%, Covestro, brand name Desmodur® BL3175SN.

[0064] HDI biuret, NCO content 17.1%, polyisocyanate, Wanhua, brand name WANNATE® 8175.

[0065] IPDI trimer, NCO content 17.0~17.5%, Evonik, brand name VESTANAT® T1890 / 100.

[0066] Vapor-phase nano-SiO2, particle size 20~30nm, specific surface area 200m² / g, Wacker.

[0067] Micron-sized SiO2, particle size 1~5μm, commercially available.

[0068] OA-POSS, octaaminoPOSS, purity ≥95%, Hybridech.

[0069] EP-POSS, octacyclic oxy POSS, Hybridech.

[0070] Vi-POSS, OctaviovinylPOSS, Hybridech.

[0071] Organized montmorillonite, with a layer thickness of 1.5 nm and an interlayer spacing of 2.5 nm, from Zhejiang Fenghong.

[0072] TPU base film, aliphatic polycaprolactone type, 150μm thick, Lubrizol.

[0073] PPPrimer, a polyolefin adhesion promoter, 10% solids content, commercially available.

[0074] TPU base film: aliphatic polycaprolactone type, 150μm thick, Lubrizol Estane 58277.

[0075] Example 1 Please see Figure 1-4 This embodiment provides a TPU base film interface anti-migration primer composition for paint protection film. The preparation method includes the following steps: 40 parts by mass of aliphatic waterborne polyurethane dispersion (PUD-A) are added to a mixing tank, along with 3 parts of KH-550 and 15 parts of ethyl acetate. The mixture is stirred at 400 rpm for 20 min at room temperature. Then, 5 parts of inorganic filler dispersion slurry are slowly added, and the stirring speed is increased to 1000 rpm for 45 min. 5 parts of HDI trimer are added, and stirring continues for 15 min. Finally, 0.5 parts of leveling agent BYK-333, 0.2 parts of defoamer BYK-024, 0.2 parts of wetting agent FC-4430, and 31.1 parts of deionized water are added. The mixture is stirred at 400 rpm for 10 min and filtered through a 300-mesh sieve to obtain the primer composition.

[0076] The preparation method of the inorganic filler dispersion slurry includes the following steps: mixing fumed nano-silica, water and ethyl acetate in a volume ratio of 1:1, and ultrasonically dispersing the mixture (ultrasonic power: 300W, ultrasonic frequency: 20kHz, ultrasonic time: 30min) to obtain the inorganic filler dispersion slurry, wherein the content of fumed nano-silica in the inorganic filler dispersion slurry is 15wt%.

[0077] The primer composition has a solid content of 20%, a viscosity of 120 mPa·s (25℃), and a surface tension of 28 mN / m.

[0078] This embodiment provides a paint protection film, the preparation method of which includes the following steps: Figure 2 As shown, a primer coating station is added between the TPU unwinding device and the functional coating section. This primer coating station includes a microgravure coating system and a short oven. A primer composition is coated on one side of the TPU base film using the microgravure coating system. The microgravure roller cell volume is 40 μm³ / cm², the coating speed is 12 m / min, and the three sections of the short oven are 70℃ / 85℃ / 105℃, with a drying time of 25 seconds for each section, resulting in a primer coating dry film thickness of 1.0 μm. Then, a self-healing polyurethane coating (25% solids content, 40 μm wet film thickness) is applied to the slit surface of the primer coating. The main oven temperature is 100℃, and drying time is 2.5 min. The self-healing polyurethane coating is then laminated with a PET protective film. A solvent-based acrylic pressure-sensitive adhesive (20% solids content, 20 μm dry adhesive thickness) is coated on the other side of the TPU base film and laminated with a matte milky white PET release film. The film is then cured at 50℃ for 36 hours to obtain a paint protective film.

[0079] Example 2 The difference between this embodiment and Embodiment 1 is that: a TPU base film interface anti-migration primer composition for paint protection film includes the following components by mass parts: 35 parts PUD-A, 4 parts KH-792 (N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane), 6 parts IPDI trimer, 2 parts inorganic filler dispersion slurry, 12 parts butyl acetate, 8 parts PMA, 0.4 parts leveling agent TEGOGlide410, 0.2 parts defoamer TEGOFoamexN, 0.2 parts wetting agent FS-3100, and 32.2 parts deionized water.

[0080] The preparation method of the inorganic filler dispersion slurry includes the following steps: mixing octaaminoPOSS (OA-POSS), a mixture of water and ethyl acetate in a volume ratio of 1:1, and performing ultrasonic dispersion treatment (ultrasonic power: 300W, ultrasonic frequency: 20kHz, ultrasonic time: 30min) to obtain the inorganic filler dispersion slurry, wherein the content of octaaminoPOSS (OA-POSS) in the inorganic filler dispersion slurry is 15wt%.

[0081] The preparation method and coating process of the TPU base film interface anti-migration primer composition for paint protection film are the same as in Example 1, and the dry film thickness of the primer layer is 1.2 μm.

[0082] Example 3 The difference between this embodiment and Embodiment 1 is that: a TPU base film interface anti-migration primer composition for paint protection film includes the following components by mass parts: PUD-B (solid content 38%, T... g =0℃, based on IPDI and polycarbonate polyol) 45 parts, 2 parts KH-550, 2 parts KH-540, 4 parts HDI biuret polyisocyanate, 3 parts HDI trimer, 1.5 parts inorganic filler dispersion slurry, 0.5 parts octacyclic POSS (EP-POSS), 10 parts ethyl acetate, 5 parts isopropanol, 0.3 parts leveling agent BYK-333, 0.15 parts defoamer BYK-024, 0.15 parts wetting agent FC-4430, 26.4 parts deionized water.

[0083] The preparation method of the inorganic filler dispersion slurry includes the following steps: mixing fumed nano-silica, water and ethyl acetate in a volume ratio of 1:1, and ultrasonically dispersing the mixture (ultrasonic power: 300W, ultrasonic frequency: 20kHz, ultrasonic time: 30min) to obtain the inorganic filler dispersion slurry, wherein the content of fumed nano-silica in the inorganic filler dispersion slurry is 15wt%.

[0084] The preparation method and coating process of the TPU base film interface anti-migration primer composition for paint protection film are the same as in Example 1, and the dry film thickness of the primer layer is 0.8 μm.

[0085] Example 4 This embodiment provides a TPU base film interface anti-migration primer composition for paint protection film, which includes the following components by weight: 30 parts PUD-A, 15 parts PUD-C, 5 parts KH-550, 8 parts HDI trimer, 2 parts inorganic filler dispersion slurry, 18 parts butyl acetate, 0.6 parts leveling agent TEGOGlide 410, 0.2 parts defoamer TEGOFoamex N, 0.2 parts wetting agent FS-3100, and 21 parts deionized water.

[0086] The preparation method of the inorganic filler dispersion slurry includes the following steps: mixing organic montmorillonite, water and ethyl acetate in a volume ratio of 1:1, and ultrasonically dispersing the mixture (ultrasonic power: 300W, ultrasonic frequency: 20kHz, ultrasonic time: 30min) to obtain the inorganic filler dispersion slurry, wherein the content of organic montmorillonite in the inorganic filler dispersion slurry is 15wt%.

[0087] The preparation method and coating process of the TPU base film interface anti-migration primer composition for paint protection film are the same as in Example 1, and the dry film thickness of the primer layer is 1.5 μm.

[0088] Example 5 This embodiment provides a TPU base film interface anti-migration primer composition for paint protection film, comprising the following components by weight: 50 parts PUD-A, 2 parts DL-602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane), 3 parts HDI trimer, 1 part octavinyl POSS, 8 parts ethyl acetate, 5 parts ethanol, 0.3 parts leveling agent BYK-333, 0.1 parts defoamer BYK-024, 0.1 parts wetting agent FC-4430, and 30.5 parts deionized water.

[0089] The preparation method of the inorganic filler dispersion slurry includes the following steps: mixing octavinyl POSS, water and ethyl acetate in a volume ratio of 1:1, and ultrasonically dispersing the mixture (ultrasonic power: 300W, ultrasonic frequency: 20kHz, ultrasonic time: 30min) to obtain the inorganic filler dispersion slurry, wherein the content of octavinyl POSS in the inorganic filler dispersion slurry is 15wt%.

[0090] The preparation method and coating process of the TPU base film interface anti-migration primer composition for paint protection film are the same as in Example 1, and the dry film thickness of the primer layer is 0.6 μm.

[0091] This embodiment is suitable for applications that require high flexibility.

[0092] Example 6 The difference between this embodiment and Example 1 is that the vapor-phase nano-SiO2 slurry is replaced with OA-POSS slurry (solid content 15wt%, dispersion medium is an equal volume mixture of water and ethyl acetate).

[0093] Example 7 The difference between this embodiment and Example 1 is that the vapor-phase nano-SiO2 slurry (15%, 5 parts) is replaced with an organic montmorillonite slurry (15wt% solid content, 5 parts, the dispersion medium is an equal volume mixture of water and ethyl acetate, ultrasonically dispersed).

[0094] Comparative Example 1 The difference between this comparative example and Example 1 is that: no primer composition is applied, and a self-healing polyurethane coating and pressure-sensitive adhesive layer are directly applied to the surface of the TPU base film (same as Example 1), while the rest of the process is the same as in Example 1.

[0095] Comparative Example 2 The difference between this comparative example and Example 1 is that only corona treatment is performed (processing power 8kW, processing speed 12m / min), the primer composition is not applied, and then a self-healing coating and pressure-sensitive adhesive layer are applied to the TPU surface after corona treatment. The rest of the process is the same as in Example 1.

[0096] Comparative Example 3 The difference between this comparative example and Example 1 is that no aminosilane coupling agent is added to the primer composition, while the rest of the formulation and process are the same as in Example 1.

[0097] Comparative Example 4 The difference between this comparative example and Example 1 is that no polyfunctional isocyanate crosslinking agent (HDI trimer) is added to the primer composition, while the rest of the formulation and process are the same as in Example 1.

[0098] Comparative Example 5 The difference between this comparative example and Example 1 is that no aminosilane coupling agent, no polyfunctional isocyanate crosslinking agent, and no nano-inorganic filler are added to the primer composition. The amounts of solvent and additives are adjusted accordingly.

[0099] The preparation method is as follows: 40 parts of PUD-A, 15 parts of ethyl acetate, and 44.1 parts of deionized water are added to a mixing tank and stirred at 400 rpm for 30 min at room temperature. Then, 0.5 parts of leveling agent BYK-333, 0.2 parts of defoamer BYK-024, and 0.2 parts of wetting agent FC-4430 are added, and stirring continues for 10 min. The mixture is then filtered through a 300-mesh sieve to obtain the primer composition. The coating process is the same as in Example 1, and the dry film thickness of the primer layer is 1.0 μm.

[0100] Comparative Example 6 The difference between this comparative example and Example 1 is that the HDI trimer in Example 1 is replaced with an equivalent amount of HDI dimer, while the rest of the formulation and process are the same as in Example 1.

[0101] Comparative Example 7 The difference between this comparative example and Example 1 is that the vapor-phase nano-SiO2 in Example 1 is replaced with an equal mass of ordinary micron-sized SiO2 (particle size 1~5μm), while the rest of the formulation and process are the same as in Example 1.

[0102] Comparative Example 8 The difference between this comparative example and Example 1 is that KH-550 in Example 1 is replaced with an equal mass of γ-glycidyl etheroxypropyltrimethoxysilane KH-560 (GPTMS, epoxysilane), while the rest of the formulation and process are the same as in Example 1.

[0103] Comparative Example 9 The difference between this comparative example and Example 1 is that: the PUD-A (T) in Example 1 is changed. g =-5℃) is replaced with the same solid content but T g =30℃ Aliphatic PUD-D, based on HDI and polycarbonate polyol, M n =25000g / mol), the rest of the formulation and process are the same as in Example 1.

[0104] Comparative Example 10 The difference between this comparative example and Example 1 is that the primer composition was replaced with a commercially available polyolefin adhesion promoter (trade name: PPPrimer, solid content 10%) as the primer, and it was applied to the surface of the TPU base film according to the supplier's recommended process (dry film thickness 1.0 μm). Then, a self-healing coating and a pressure-sensitive adhesive layer were applied, and the rest of the process was the same as in Example 1.

[0105] Comparative Example 11 The difference between this comparative example and Example 1 is that PUD-A in Example 1 is replaced with an equal mass of PUD-E (40% solid content, T...). g =-5℃, prepared based on HDI and polyether polyol PTMG1000, number average molecular weight M n =35000g / mol), the remaining components, dosages and preparation methods are the same as in Example 1.

[0106] Comparative Example 12 The difference between this comparative example and Example 1 is that the HDI trimer (5 parts) in Example 1 is replaced with the aziridine crosslinking agent TMP-TMAZ (3 parts, functionality = 3, active ingredient content 70%, solvent is deionized water), while the remaining components, dosages, and preparation methods are the same as in Example 1. The above substitution refers to the conversion based on the equivalent molar number of active crosslinking groups.

[0107] Comparative Example 13 The difference between this comparative example and Example 1 is that the vapor-phase nano-SiO2 is replaced with an equal mass of nano-calcium carbonate (particle size 30~50nm), and the dispersion medium and dispersion process are the same as in Example 1.

[0108] Comparative Example 14 The difference between this comparative example and Example 1 is that the vapor-phase nano-SiO2 is replaced with an equal mass of nano-titanium dioxide (rutile type, particle size 20~30nm), and the dispersion medium and dispersion process are the same as in Example 1.

[0109] Comparative Example 15 The difference between this comparative example and Example 1 is that the amount of KH-550 is reduced from 3 parts to 0.5 parts, while the other components remain unchanged.

[0110] Comparative Example 16 The difference between this comparative example and Example 1 is that the amount of KH-550 is increased from 3 parts to 8 parts, while the other components remain unchanged.

[0111] Comparative Example 17 The difference between this comparative example and Example 1 is that the amount of HDI trimer is reduced from 5 parts to 1 part, while the other components remain unchanged.

[0112] Comparative Example 18 The difference between this comparative example and Example 1 is that the amount of PUD-A was reduced from 40 parts to 20 parts, and the amount of deionized water was increased accordingly to keep the solid content within the operable range (solid content kept at 15%), while the other components remained unchanged.

[0113] Comparative Example 19 The difference between this comparative example and Example 1 is that the vapor-phase nano-SiO2 slurry (15%, 5 parts) was replaced with an equal mass of water and ethyl acetate mixture (without filler), while the other components remained unchanged.

[0114] Comparative Example 20 The difference between this comparative example and Example 1 is that the amount of vapor-phase nano-SiO2 slurry is increased from 5 parts to 20 parts, while the other components remain unchanged.

[0115] Comparative Example 21 The difference between this comparative example and Example 1 is that PUD-A is replaced with PUD-H (solid content 40%, T...). g =-5℃, based on HDI and polycaprolactone polyol, M n =10000g / mol), the other components, dosages and preparation methods are the same as in Example 1.

[0116] Comparative Example 22 The difference between this comparative example and Example 1 is that PUD-A is replaced with PUD-I (solid content 40%, T g =-5℃, based on HDI and polycaprolactone polyol, M n =15000g / mol), the remaining components, dosages and preparation methods are the same as in Example 1.

[0117] Comparative Example 23 The difference between this comparative example and Example 1 is that PUD-A is replaced with PUD-J (solid content 40%, T...). g =-5℃, based on HDI and polycaprolactone polyol, M n =80000g / mol), the remaining components, dosages and preparation methods are the same as in Example 1.

[0118] Comparative Example 24 The difference between this comparative example and Example 1 is that PUD-A in Example 1 is replaced with PUD-K (solid content 40%, T...). g =-5℃, based on HDI and polycaprolactone polyol, M n =100000g / mol), the remaining components, dosages and preparation methods are the same as in Example 1.

[0119] Performance testing: The following performance tests were conducted on the paint protective films prepared in Examples 1-7 and Comparative Examples 1-24 above: (1) Anti-precipitation performance: According to the TCSTM01150-2024 standard, the sample was placed in an 80℃ oven for 24 hours and then cooled. The haze increase ΔH (%) was measured using a haze meter (BYKHaze-gardplus), and the surface was visually observed for any precipitates. (2) Interlayer peel strength: The 180° peel strength (N / 25mm) of the repair coating / primer / TPU three-layer system was measured according to ASTM D903-98(2025) standard, with a tensile rate of 300mm / min; (3) Pressure-sensitive adhesive peel strength: According to GB / T2792-2014 standard, the 180° peel strength (N / 25mm) of the pressure-sensitive adhesive layer / primer / TPU three-layer system was measured. (4) Holding power attenuation rate: According to GB / T4851-2014 standard, the holding power (min) of the sample before and after heat aging at 85℃ / 1000h was measured, and the attenuation rate (%) was calculated as follows: (holding power before heat aging - holding power after heat aging) ÷ holding power before heat aging × 100%; (5) Missing coating defect rate: Under the production condition of coating speed of 12m / min, the percentage of pinholes and missing coating points on the surface of the repaired coating was statistically analyzed using an online CCD vision inspection system. (6) Light transmittance and haze: measured using a haze meter in accordance with GB / T2410-2008 standard.

[0120] The test results are shown in Table 1.

[0121]

[0122]

[0123] As shown in Table 1, the anti-exudation ΔH of the protective films in Examples 1-7 is 0.3%~0.8%, which is far superior to the requirements of industry standard TCSTM01150-2024 (≤2.0%); the interlayer peel strength is 9.5N / 25mm~14.8N / 25mm; the pressure-sensitive adhesive peel strength is 11.5N / 25mm~17.5N / 25mm; the holding power attenuation rate is 6.1%~12.2%; the missing coating defect rate is 0.03%~0.15%; and the light transmittance is 90.8%~92.5%.

[0124] The results show that the lamellar structure of montmorillonite is oriented parallel to the base film surface in the coating, and small molecule additives must bypass the lamellar structure to migrate to the surface (tortuosity effect), resulting in excellent anti-exudation performance. In the products of this invention, POSS and nano-SiO2 are more suitable as inorganic fillers for car wrap products with high optical requirements; for applications where anti-exudation performance is prioritized and optical requirements are secondary, montmorillonite is a feasible alternative. The comprehensive performance of the above three inorganic fillers meets the requirements of high light transmittance, high gloss, low residual adhesive rate, aging resistance, high puncture resistance, and high tensile strength for paint protection films.

[0125] Compared with Comparative Example 1 (without primer) and Comparative Example 2 (with only corona treatment), the products of Examples 1-7 showed significant improvements in all key performance indicators, including anti-exudation properties, interlayer peel strength, pressure-sensitive adhesive peel strength, tack retention rate, and missing coating defect rate. This indicates that the primer composition and coating method of the present invention can effectively solve the interface problem caused by the migration of TPU base film additives.

[0126] The interlayer peel strength of Comparative Example 3 without silane coupling agent was lower than that of Example 1, and the tack hold at 85°C / 1000h was nearly twice that of Example 1, indicating that chemical anchoring is crucial for improving the interfacial adhesion and long-term stability between the base coating and TPU. It is noteworthy that the short-term anti-exudation effect of Comparative Example 3 was similar to that of Example 1, suggesting that physical barriers themselves can provide good short-term anti-exudation effects, but the interface lacking chemical anchoring will significantly deteriorate under long-term thermal aging.

[0127] Comparative Example 4 showed a significant deterioration in its anti-exudation performance and tack retention rate without crosslinking agent. Although the interlayer peel strength was still acceptable, it indicates that the physical barrier function is indispensable for inhibiting the migration of additives and maintaining long-term stability.

[0128] Comparative Example 5, with only PUD primer, still exceeded the industry standard requirements for anti-exudation performance (≤2.0%), but its interlayer peel strength was much lower than that of Example 1, and its missing coating defect rate was also significantly higher than that of Example 1.

[0129] Comparative Example 6 demonstrates that trifunctional or higher crosslinking agents are a necessary condition for constructing a dense three-dimensional barrier network. Difunctional crosslinking agents can only form linear chain growth and cannot achieve true three-dimensional crosslinking, resulting in a significant deterioration in both density and barrier effect.

[0130] In Comparative Example 7, after replacing nano-SiO2 with micro-SiO2, the micro-filler could not be uniformly dispersed in the gaps of the cross-linked network, forming local pores and reducing the barrier effect; at the same time, the micro-filler scattered visible light, significantly reducing the light transmittance of the coating; in addition, the micro-filler damaged the surface smoothness of the coating, affecting the uniform coating of the upper layer.

[0131] In Comparative Example 8, replacing aminosilane with epoxysilane resulted in decreased interlayer peel strength, increased anti-precipitation ΔH, and increased tack decay rate. Analysis suggests that the epoxy groups have lower reactivity with the isocyanate groups on the TPU surface than the amino groups, and the epoxy groups do not participate in the isocyanate crosslinking reaction, thus failing to act as crosslinking network nodes to achieve the coupling of chemical anchoring and physical barrier.

[0132] Comparative Example 9 uses PUD-A(T) g =-5℃) replace with PUD-D(T g After reaching 30℃, the interlayer peel strength decreased, and the rate of missing coating increased. Analysis shows that... g Excessive PUD results in poor film formation at room temperature, reduced molecular chain mobility, decreased segment miscibility with TPU soft segments, leading to deterioration of interfacial compatibility and adhesion.

[0133] Comparative Example 10 used a commercially available polyolefin adhesion promoter as a primer, and all indicators were far inferior to those of the embodiments of the present invention, proving that the primer composition of the present invention has significant technical advantages compared with the prior art.

[0134] Comparative Example 11 shows that the chemical structure similarity between the PUD prepared from polyether polyol and the polycaprolactone-based TPU film is low. The TPU soft segments have a polyester structure, while the PUD soft segments have a polyether structure. The reduced segment miscibility between the two soft segments leads to a decrease in the molecular entanglement density at the interface. Furthermore, the UV resistance and oxidation resistance of the polyether segments are inferior to those of the polycaprolactone segments, and the interfacial properties degrade more rapidly after long-term thermal aging. This indicates that the silane coupling agent, crosslinking agent + filler, and the miscibility between the PUD matrix and the TPU base film have a synergistic effect. Only when PUD and TPU have a certain degree of compatibility can the silane coupling agent be uniformly distributed in the interfacial region, and the crosslinking network forms effective topological entanglement with the TPU molecular chains, thereby improving the dual functions of chemical anchoring and physical barrier.

[0135] Comparative Example 12 illustrates that the effect of using aziridine crosslinking agent is worse than that of using PUD. The analysis is that the crosslinking point density of aziridine and PUD is low, which makes it impossible to form a sufficiently dense three-dimensional network. Aziridine does not participate in the hydrolysis and condensation reaction of silane coupling agent, and cannot form an organic-inorganic hybrid network. There is a lack of coupling effect between chemical anchoring and physical barrier. At the same time, the optimal reaction temperature of aziridine does not match the high-temperature section of the three-stage short oven process. At this temperature, aziridine may undergo side reactions or decomposition, affecting the uniformity of crosslinking.

[0136] In Comparative Example 13, due to the lack of active groups such as silanol groups on the surface of CaCO3, it cannot participate in the hydrolysis and condensation network of aminosilane coupling agent and the cross-linking network of isocyanate, and can only be a physical filler; its surface alkalinity also interferes with the uniformity of the isocyanate cross-linking reaction; the nano CaCO3 has poor dispersion stability, is easy to agglomerate and form pores, and its refractive index is very different from that of the PUD matrix, resulting in a significant deterioration in optical performance.

[0137] The strong light-blocking properties of TiO2 in Comparative Example 14 conflict with the high transparency requirements of car wraps; more importantly, its photocatalytic activity accelerates the photo-oxidative aging of the PUD substrate and interface layer, leading to accelerated interface performance degradation after long-term use and making long-term interface stability impossible. Comparative Examples 13 and 14 demonstrate that only the surface chemical activity of the inorganic filler selected in this invention can achieve the excellent optical properties and weather resistance of the protective film.

[0138] In Comparative Example 15, the amino group density was insufficient to form a uniform chemical anchoring layer on the TPU surface. Although the physical barrier effect could still maintain good short-term anti-exudation performance, the lack of sufficient chemical bonding at the interface led to a significant decrease in adhesion after long-term thermal aging.

[0139] In Comparative Example 16, excessive silane coupling agent underwent excessive hydrolysis and condensation during the storage and drying of the primer, forming localized Si-O-Si aggregates. This resulted in microscopic inhomogeneity of the coating and a shortened pot life. Furthermore, silane coupling agent is expensive, and excessive addition is uneconomical.

[0140] In Comparative Example 17, the use of 1 part of HDI trimer resulted in insufficient crosslinking density, allowing low molecular weight additives to penetrate freely. This led to insufficient coating density, preventing the nanofillers from being effectively anchored in the crosslinking network, which could result in filler migration or agglomeration.

[0141] In Comparative Example 18, 20 parts of PUD provided only about 8% PUD solids in the dry film, which was insufficient to form a continuous and uniform film. Instead, it resulted in a porous and discontinuous coating with low interface coverage. When the PUD matrix was insufficient, the dispersion stability of the nanofiller decreased, and agglomeration and sedimentation were prone to occur.

[0142] In Comparative Example 19, without the addition of inorganic fillers, the tack retention rate and the rate of missing coating defects increased significantly.

[0143] While excessive nanofillers in Comparative Example 20 may further enhance the barrier effect, they can lead to deterioration of optical properties and reduced light transmittance; decreased dispersion stability and potential local agglomeration; and excessive rigid inorganic fillers can weaken the flexibility and tensile properties of the coating.

[0144] Comparative Examples 21-24 show that PUD parameters have a significant impact on product performance. Insufficiently short PUD molecular chain length leads to insufficient film strength and a risk of excessive cross-linking, resulting in excessive coating rigidity and increased brittleness, making it prone to cracking under stress. Low molecular weight PUDs have high concentrations of terminal groups, increasing the free volume near the chain ends and providing additional channels for the migration of low molecular weight additives. Simultaneously, the insufficient entanglement length between short-chain PUDs and TPU molecular chains weakens the topological constraint effect at the interface, allowing additives to easily escape. Excessively long PUD molecular chains reduce chain mobility, preventing the achievement of thermodynamic equilibrium and miscibility at room temperature. Excessively high primer viscosity leads to uneven coating and reduced transfer efficiency. Incomplete film aggregation may leave residual microparticle boundaries in the coating, forming potential pores. In high molecular weight matrices, the diffusion coefficient of the cross-linking agent decreases, resulting in uneven cross-linking reactions and excessively low or high local cross-linking densities, affecting the overall density of the barrier network.

[0145] pass Figure 5-13 It can be seen that the paint protection film repair coating prepared by this invention is firmly bonded to the TPU base film through the primer layer, and the coating has low permeability, which does not easily cause the exudation of additives in the TPU base film and affect the adhesion of the adhesive layer. In Comparative Example 1, there are obvious gaps at the interface, and the repair coating is poorly bonded to the TPU base film; a large number of bright-colored particulate exudates can be seen at the interface, which are TPU additives that migrate and precipitate, and are unevenly distributed and severely aggregated. After corona treatment, Comparative Example 2 has many pores at the interface, and the bonding is still not tight; a large number of exudates can be seen adhering to the interface, and there are obvious pores, which can easily lead to coating defects. Comparative Example 3 has no silane coupling agent, lacks chemical anchoring, and has low interface bonding strength; local delamination and interface gaps can be seen, and a small amount of exudates are distributed relatively evenly. Comparative Example 4 has no crosslinking agent, the primer layer has poor density and a porous structure; many pores and exudates can be seen, the additives are easy to migrate, and the long-term stability is poor. Comparative Example 5 only used PUD to form a film, which was discontinuous and poorly compacted; visible micropores and a large number of precipitates were present, with no effective barrier effect and weak interfacial bonding.

[0146] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A TPU base film interface anti-migration primer composition for paint protection film, characterized in that, The composition comprises, by weight, the following components: 30-50 parts of aliphatic waterborne polyurethane dispersion; 2-5 parts of aminosilane coupling agent; 3-8 parts of multifunctional aliphatic isocyanate crosslinking agent; 1-10 parts of inorganic filler dispersion slurry; 10-25 parts of organic solvent; and 30-50 parts of deionized water; wherein the inorganic filler in the inorganic filler dispersion slurry accounts for 0.2%-5% of the total mass of the composition; the aliphatic waterborne polyurethane dispersion is prepared by reacting aliphatic diisocyanate with polycaprolactone polyol and / or polycarbonate polyol; the solid content of the aliphatic waterborne polyurethane dispersion is 35%-45%, and the glass transition temperature T0 is... g Temperature range: -20℃ to 10℃; Number average molecular weight: 20,000 to 60,000 g / mol.

2. The TPU base film interface anti-migration primer composition for paint protection film according to claim 1, characterized in that, The aminosilane coupling agent is selected from one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, or N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane.

3. The TPU base film interface anti-migration primer composition for paint protection film according to claim 1, characterized in that, The functionality of the multifunctional aliphatic isocyanate crosslinking agent is ≥3.

4. The TPU base film interface anti-migration primer composition for paint protection film according to claim 3, characterized in that, The multifunctional aliphatic isocyanate crosslinking agent is selected from one or more of hexamethylene diisocyanate trimer, HDI biuret polyisocyanate, isophorone diisocyanate trimer, or HDI / IPDI mixed trimer.

5. The TPU base film interface anti-migration primer composition for paint protection film according to claim 1, characterized in that, The nano-inorganic filler is selected from one or more of the following: fumed silica, cage-shaped polysilsesquioxane, and surface-modified nano-layered silicates.

6. The TPU base film interface anti-migration primer composition for paint protection film according to claim 1, characterized in that, The organic solvent is selected from one or more of ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, isopropanol, n-butanol, or ethanol.

7. A method for applying the primer composition according to any one of claims 1 to 6, characterized in that, Includes the following steps: (1) The primer composition is uniformly coated on the surface of the TPU base film to form a primer layer; (2) The TPU base film after the primer composition is coated is dried and cured to obtain the TPU base film after primer treatment.

8. The application of the TPU base film interface anti-migration primer composition for paint protection film according to any one of claims 1 to 6, characterized in that, The anti-migration primer composition is used to prepare a protective film for paint surfaces.

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