Scratch-resistant release film and preparation method thereof

Abstract

The invention discloses a scratch-resistant release film, which is composed of a base material layer and a release coating, the base material layer comprises the following components by mass: 80-95 parts of PET resin, 5-15 parts of thermoplastic polyurethane, 1-5 parts of a flexibilizer, 0.1-0.5 part of a pentaerythritol ester antioxidant, and 1-3 parts of a POE-g-MAH compatibilizer; the release coating is prepared from the following components in parts by mass: 30 to 50 parts of an organic silicon release agent, 10 to 20 parts of a wear-resistant auxiliary agent, 2 to 5 parts of a cross-linking agent, 0.1 to 0.5 part of a catalyst, 2 to 5 parts of ethyoxyl polysilazane and 80 to 120 parts of a solvent; the wear-resistant additive comprises polytetrafluoroethylene micro powder and organic surface modified boron nitride, and the solvent is a mixed solvent of ethyl acetate and isopropanol; the release film prepared from the components has both flexibility and scratch resistance.

Description

Technical Field

[0001] This application relates to the field of functional thin film materials technology, and in particular to a scratch-resistant release film and its preparation method. Background Technology

[0002] Release films, as a functional protective material, are widely used for temporary protection of automotive and electronic products due to their peelability and smooth surface. Most existing release films use polyethylene terephthalate (PET) as the base material, with a low surface energy coating formed by coating the surface with silicone, fluorine, or non-silicone release agents. Among these, silicone release films dominate the market due to their excellent release force stability and temperature resistance; their coatings are achieved through solvent-based or solvent-free processes, with the latter gradually becoming an industry trend due to its environmental advantages. Fluorine release films are characterized by ultra-low surface energy and chemical corrosion resistance, but their higher cost limits their application. Non-silicone release systems attempt to balance release performance and residual adhesive rate through modification with acrylates or polyurethanes, but their long-term temperature resistance is still inferior to silicone systems.

[0003] However, traditional release films struggle to combine scratch resistance with high flexibility. To improve scratch resistance, traditional release films typically increase coating hardness or introduce inorganic fillers (such as silica or alumina). However, this increases coating brittleness, making it prone to cracking or even peeling under bending or dynamic stress. Conversely, if flexibility is enhanced by reducing coating crosslinking or adding elastomers, the surface hardness of the coating decreases, making it unable to effectively resist scratches from sharp objects. Summary of the Invention

[0004] To address the issue that traditional release films struggle to combine scratch resistance with high flexibility, a scratch-resistant release film and its preparation method are provided.

[0005] The above-mentioned objective of this invention is achieved through the following technical solutions: A scratch-resistant release film, comprising a substrate layer and a release coating layer. The substrate layer comprises the following components in parts by weight: 80-95 parts of PET resin, 5-15 parts of thermoplastic polyurethane, 1-5 parts toughening agent Pentylenetetraethylene glycol ester antioxidant, 0.1~0.5 parts. 1-3 parts of POE-g-MAH compatibilizer; The release coating comprises the following components in parts by weight: 30-50 parts of silicone release agent 10-20 parts of wear-resistant additive, 2-5 parts of crosslinking agent Catalyst 0.1~0.5 parts, 2-5 parts of ethoxylated polysilazane Solvent 80-120 parts; Wear-resistant additives include polytetrafluoroethylene micro powder and organically surface-modified boron nitride. The solvent is a mixture of ethyl acetate and isopropanol.

[0006] By adopting the above technical solutions, the PET resin in the substrate layer provides rigidity as the main skeleton, and the introduction of thermoplastic polyurethane, through the soft segments in its molecular chain forming a partially compatible microphase separation structure with PET, endows the substrate layer with inherent toughness; the toughening agent, through its core-shell structure, forms an elastic dispersed phase in the PET matrix, absorbing external stress and inhibiting crack propagation through crazing and shear banding mechanisms; the anhydride groups in the POE-g-MAH compatibilizer react with the terminal hydroxyl or carboxyl groups of PET, while its polyolefin segments are compatible with TPU and the toughening agent, forming a strong interfacial bond, avoiding performance degradation caused by phase separation; the pentaerythritol ester antioxidant inhibits oxidative degradation during high-temperature processing by capturing free radicals, maintaining the integrity of the molecular chain; the silicone release agent in the release coating has low surface energy, making the surface smooth and non-stick; the polytetrafluoroethylene micropowder forms a lubricating layer on the coating surface through its low coefficient of friction and layered structure, and the organic surface... Modified boron nitride, with its high hardness and layered structure, is dispersed in an organosilicon network, resisting scratches through physical barrier and stress dispersion. The main chain of ethoxy polysilazane is dominated by Si-N bonds, while the side chains contain organic groups such as ethoxy groups. These ethoxy groups undergo hydrolysis to generate active silanol groups, which then undergo condensation reactions with Si-H or Si-NH to form strong siloxane bonds, tightly connecting the components in the coating and forming an organic-inorganic hybrid network that gives the coating both wear resistance and flexibility. The crosslinking agent undergoes a hydrosilylation reaction with the organosilicon to form a three-dimensional network. The catalyst regulates the reaction rate. The mixed solvent of ethyl acetate and isopropanol ensures uniform dispersion of the components and applicability of the coating. The substrate layer achieves high flexibility and tear resistance through multi-component synergistic toughening. The release coating significantly improves surface hardness and scratch resistance through wear-resistant additives and a highly crosslinked network, making the overall film layer less prone to cracking or scratching under bending or external friction.

[0007] Optionally, the mass ratio of polytetrafluoroethylene micro powder to organic surface-modified boron nitride is (1~2):1.

[0008] By adopting the above technical solution, polytetrafluoroethylene (PTFE) micropowder reduces friction during scraping through lubrication, while boron nitride disperses stress through its high hardness and layered structure. The optimized ratio of the two forms a complementary relationship: too much PTFE micropowder may lead to a decrease in coating strength, while too much boron nitride is prone to agglomeration. At this ratio, the two are uniformly dispersed in the organosilicon system. PTFE micropowder fills the gaps between boron nitride layers and synergistically forms a continuous protective layer, enabling the coating to have both low friction coefficient and wear resistance.

[0009] Optionally, the toughening agent is a methyl methacrylate-butadiene-styrene copolymer.

[0010] By adopting the above technical solution, the butadiene rubber core of the methyl methacrylate-butadiene-styrene copolymer is an elastomer in its core-shell structure, and the styrene-methyl methacrylate shell is compatible with PET resin. When the substrate is subjected to external force, the methyl methacrylate-butadiene-styrene copolymer particles act as stress concentration points, inducing crazes and shear bands, absorbing energy and preventing crack propagation. The flexibility of the release film is improved, and it is not easy to break brittlely.

[0011] Optionally, the organic surface-modified boron nitride is vinyl-modified boron nitride.

[0012] By adopting the above technical solution, the vinyl functional groups on the surface of vinyl-modified boron nitride can directly participate in the hydrosilylation reaction of organosilicon release agent. When subjected to scratching force, vinyl-modified boron nitride can be more firmly fixed in the coating and is not easy to fall off, thereby improving the scratch resistance of the coating.

[0013] Optionally, vinyl-modified boron nitride is obtained by modification with a vinyltriethoxysilane coupling agent.

[0014] By adopting the above technical solution, the vinyltriethoxysilane coupling agent has a slower hydrolysis rate, which effectively avoids problems such as viscosity surge, filler re-agglomeration or poor coating leveling caused by excessively fast reaction, and makes boron nitride more uniformly distributed in the coating.

[0015] Optionally, the crosslinking agent is polymethylhydrosiloxane.

[0016] By adopting the above technical solution, polymethylhydrosiloxane can be well compatible with other components in the release coating, such as organosilicon release agents, wear-resistant additives, and solvents. In the release coating, polymethylhydrosiloxane can undergo hydrosilylation reaction with the silicon-hydrogen bonds in the organosilicon release agent to form a cross-linked structure, which connects the molecular chains in the coating to form a three-dimensional network, thereby improving the hardness and wear resistance of the coating. At the same time, the cross-linked structure can also restrict the movement of molecular chains, reduce the plastic deformation of the coating during the scratching process, and enhance the scratch resistance of the coating.

[0017] Optionally, the catalyst is a delayed platinum catalyst.

[0018] By adopting the above technical solution, the catalyst is a delayed platinum catalyst, which has low activity at room temperature and rapidly releases platinum active centers during high-temperature curing to catalyze the hydrosilylation reaction, resulting in stability before coating and complete reaction during curing, indirectly improving the flexibility and scratch resistance of the release film.

[0019] The second objective of this invention is achieved through the following technical solution: The preparation method of any of the above-mentioned scratch-resistant release films includes the following steps: S1: PET resin, thermoplastic polyurethane, toughening agent, pentaerythritol ester antioxidant, and POE-g-MAH compatibilizer are mixed to obtain a premix; the premix is ​​fed into a twin-screw extruder, extruded, cast into a film, stretched and shaped, and cooled to obtain a modified PET substrate. S2: Add organosilicon release agent, wear-resistant additive, crosslinking agent, catalyst, and ethoxy polysilazane to a mixed solvent, stir, disperse, and obtain release coating liquid; S3: Apply release coating liquid to one side of the modified PET substrate and cure the coated substrate.

[0020] By adopting the above technical solution, the substrate achieves molecular-level dispersion of each component through twin-screw extrusion, stretching and shaping to enhance the molecular chain arrangement and improve the mechanical properties of the substrate. The release coating liquid is dispersed to ensure uniform distribution of wear-resistant additives. After curing, it forms a continuous protective layer, allowing the components to play their full role and realizing the structural integration of the substrate and coating, synergistically improving the overall flexibility and scratch resistance.

[0021] In summary, this application has at least the following beneficial effects: (1) The ethoxy groups of ethoxy polysilazane hydrolyze to generate active silanol groups, and the silanol groups form siloxane bonds, which make the components in the coating form an organic-inorganic hybrid network, so that the coating has both wear resistance and flexibility. (2) Organic surface-modified boron nitride, with its high hardness and layered structure, can be uniformly dispersed in the organic system and resists scratching through physical barrier and stress dispersion. (3) Polytetrafluoroethylene micro powder fills the gaps between boron nitride layers and works together to form a continuous protective layer, so that the coating has both low friction coefficient and wear resistance. Detailed Implementation

[0022] raw material PET resin, grade Sinopec Yizheng Chemical Fiber BG80, intrinsic viscosity 0.796 dl / g, purchased from Sinopec Yizheng Chemical Fiber; Thermoplastic polyurethane, a polyester-type TPU, was purchased from Zhejiang Huafeng Thermoplastic Polyurethane Co., Ltd. The methyl methacrylate-butadiene-styrene copolymer was prepared by emulsion grafting of methyl methacrylate (40%), styrene-butadiene latex (30%), and styrene (30%), and was purchased from Shanghai Better Chemical Co., Ltd. Styrene-butadiene block copolymer, model ZL-H3591, was purchased from Zhejiang Zhongli Synthetic Materials Technology Co., Ltd. Ethylene propylene diene monomer (EPDM) rubber, Sinopec Mitsui EPDM3092PM, was purchased from Shanghai Sinopec Mitsui Chemical Co., Ltd. The four-period pentylene ester antioxidant, brand name RIANOX® 1010, was purchased from Tianjin Lianlong New Materials Co., Ltd. POE-g-MAH compatibilizer, brand name Fine-Blend® FB521A, was purchased from Jia Yi Rong Polymer (Shanghai) Co., Ltd. The silicone release agent, model SH-620, with a viscosity of 180~250 mPa.s, was purchased from Hubei Longsheng Sihai New Materials Co., Ltd. Polytetrafluoroethylene micro powder, with an average particle size of 3µm, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Boron nitride, in the form of boron nitride nanopowder, with a purity ≥98.0wt% and B2O3 ≤0.5wt%, was purchased from Suzhou Napo Materials Technology Co., Ltd. Vinyltriethoxysilane (product number JH-V151), 3-aminopropyltriethoxysilane (product number JH-A110), 3-mercaptopropyltrimethoxysilane (product number JH-S189), vinyltrimethoxysilane (product number JH-V171), and vinyltriisopropoxysilane (product number JH-V173) were all purchased from Hubei Jianghan New Materials Co., Ltd. The polymethylhydrosiloxane, a hydrogen-terminated series, model D-50, with a viscosity of 60 mPa·s and a hydrogen content of 0.05wt%, was purchased from Jiangsu Kexing New Materials Co., Ltd. The isocyanate crosslinking agent, brand name Trixene® BI7982, isocyanate type is HDI biuret, the blocking agent is DMP dimethyl phthalate, viscosity at 25℃ is 600 mPa.s, solid content is 70wt%, purchased from Shanghai Juncai Materials Technology Co., Ltd. Methyltrimethoxysilane, purity ≥98wt%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Delayed platinum catalyst, purity ≥99wt%, purchased from Dongguan Yaneng Organosilicon Materials Co., Ltd. Dibutyltin dilaurate, purity ≥94.5wt%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Methyldichlorosilane, purity ≥99.8wt%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Dimethyldichlorosilane, purity ≥99wt%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Ethyl acetate, isopropanol, anhydrous n-hexane, and anhydrous ethanol were all sourced from commercially available sources.

[0023] Preparation Example 1 An ethoxylated polysilazane, the preparation method of which is as follows: The reactor was evacuated to a vacuum of 8 Pa. Under the protective atmosphere of argon, 5 L of anhydrous n-hexane was added to the reactor and stirred at 200 rpm. 640 g of methyldichlorosilane and 715 g of dimethyldichlorosilane were mixed and added dropwise to the reactor at a rate of 10 mL / min. The temperature was maintained at -20 °C to obtain the reaction solution.

[0024] Insert the ammonia gas delivery tube below the liquid surface and introduce ammonia gas at a rate of 100 mL / min for 5 hours. Then stop introducing ammonia gas and allow the reaction solution to naturally heat up to room temperature (25°C). Stir at 100 rpm for 12 hours at room temperature. Use a G4 sintered glass funnel for vacuum filtration to obtain a filter cake. Wash the filter cake three times with anhydrous n-hexane. Add the washed anhydrous n-hexane to the filtrate to obtain a mixed filtrate.

[0025] The mixed filtrate was placed in a reaction flask, and the temperature inside the flask was cooled to 0℃. 1.1 kg of anhydrous ethanol was added dropwise to the mixed filtrate at a rate of 1 mL / s. The temperature inside the reaction flask was raised to 70℃ at a rate of 10℃ / min and maintained at 70℃ for 24 h. After naturally cooling to room temperature (25℃), the mixture was filtered through a G4 sintered glass funnel to remove solid particles and obtain the final filtrate. The final filtrate was distilled for 20 min in a 50℃ water bath at -0.095 MPa to remove n-hexane and ethanol. Low-boiling-point byproducts were removed by distilling in an 80℃ water bath for 15 min to obtain a liquid ethoxylated polysilazane.

[0026] Preparation Example 2 An organic surface-modified boron nitride is prepared by the following method: Add 400g of vinyltriethoxysilane to 30L of anhydrous ethanol at a rate of 20mL / min while stirring at 100rpm. Add 2.28L of deionized water and 15mL of glacial acetic acid and stir at 200rpm for 45min to obtain an ethanol-water solution of vinyltriethoxysilane coupling agent.

[0027] Add 10 kg of boron nitride powder to the reactor, add 50 L of ethanol, turn on the high-speed disperser, and disperse at 2000 rpm for 30 min. Add the vinyltriethoxysilane coupling agent ethanol aqueous solution to the reactor, stir at 150 rpm for 15 min, heat the reactor to 78°C at 2°C / min, stir at 80 rpm for 8 h at this temperature, and let it cool naturally to 40°C to obtain the reaction material.

[0028] The reaction mixture was subjected to solid-liquid separation using a centrifuge at 2500 rpm to obtain a filter cake. The filter cake was washed with anhydrous ethanol, and the centrifugation and anhydrous ethanol washing process was repeated four times. The washed wet filter cake was then spread on a dryer tray to a thickness of 3 cm. The drying temperature was set to 80℃ and the vacuum degree to -0.095 MPa, and the drying was carried out for 24 hours. After being pulverized, an organic surface-modified boron nitride was obtained.

[0029] Preparation Example 3 An organic surface-modified boron nitride differs from Preparation Example 2 in that: 3-aminopropyltriethoxysilane is used in equimolar amounts instead of vinyltriethoxysilane; the rest is the same as Preparation Example 2.

[0030] Preparation Example 4 An organic surface-modified boron nitride differs from Preparation Example 2 in that: 3-mercaptopropyltrimethoxysilane is used in equimolar amounts instead of vinyltriethoxysilane; the rest is the same as Preparation Example 2.

[0031] Preparation Example 5 An organic surface-modified boron nitride differs from Preparation Example 2 in that: vinyltrimethoxysilane is used in equimolar amounts instead of vinyltriethoxysilane; the rest is the same as Preparation Example 2.

[0032] Preparation Example 6 An organic surface-modified boron nitride differs from Preparation Example 2 in that: vinyltriisopropoxysilane is used in equimolar amounts instead of vinyltriethoxysilane; the rest is the same as Preparation Example 2.

[0033] Example 1 A scratch-resistant release film comprises a substrate layer and a release coating. The substrate layer is prepared from the following raw material components: 90 kg of PET resin, 10 kg of thermoplastic polyurethane, 3 kg of methyl methacrylate-butadiene-styrene copolymer, 0.3 kg of pentaerythritol ester antioxidant, and 2 kg of POE-g-MAH compatibilizer. The release coating is prepared from the following raw material components: 40 kg of silicone release agent, 9 kg of polytetrafluoroethylene micro powder, 6 kg of organic surface-modified boron nitride, 3 kg of polymethylhydrosiloxane, 0.3 kg of delayed platinum catalyst, 3 kg of ethoxy polysilazane, 75 kg of ethyl acetate, and 25 kg of isopropanol. The ethoxy polysilazane is derived from Preparation Example 1, and the organic surface-modified boron nitride is derived from Preparation Example 2.

[0034] Its preparation method is as follows: S1: PET resin, thermoplastic polyurethane, methyl methacrylate-butadiene-styrene copolymer, pentaerythritol ester antioxidant, and POE-g-MAH compatibilizer are mixed at 1000 rpm and 90±1℃ for 20 min to obtain a premix. The premix is ​​fed into a twin-screw extruder at 350 rpm. The melt in the twin-screw extruder is extruded through a T-die and cast onto the surface of a 25℃ cooling roller to form a 200µm film. The film is then biaxially stretched and shaped to obtain a modified PET substrate with a thickness of 40±1µm. The length-to-diameter ratio of the twin-screw extruder is 40:1, and the segmented temperatures are set as follows: Zone 1 255℃, Zone 2 265℃, Zone 3 275℃, and Die 280℃. S2: Ethyl acetate and isopropanol were mixed to obtain a mixed solvent. Organosilicon release agent, polytetrafluoroethylene micro powder, organic surface-modified boron nitride, polymethylhydrosiloxane, and ethoxy polysilazane were added to the mixed solvent and stirred at 600 rpm for 20 min. Delayed platinum catalyst was added and stirred at 600 rpm for 10 min. The mixture was then treated with an ultrasonic disperser for 12 min. The ultrasonic disperser power was 400W to obtain the release coating liquid. S3: Using a micro-gravure coating machine (180 lines / inch, cell depth 30μm), coating speed 10m / min, substrate tension 15N / m, the release coating liquid is applied to one side of the modified PET substrate. The coated substrate is placed in a curing oven and cured at 90℃ for 10min, then at 130℃ for 25min to form the final product. The curing oven wind speed is 5m / s, the coating thickness is 5μm, and it is naturally cooled to room temperature (25℃) to obtain a scratch-resistant release film.

[0035] Comparative Example 1 A scratch-resistant release film differs from Example 1 in that it does not contain ethoxylated polysilazane; the rest is the same as Example 1.

[0036] Comparative Example 2 A scratch-resistant release film differs from Example 1 in that it uses boron nitride of equal mass instead of organic surface-modified boron nitride; the rest is the same as Example 1.

[0037] Example 2 A scratch-resistant release film differs from Example 1 in that it contains 7.5 kg of polytetrafluoroethylene micro powder and 7.5 kg of organic surface-modified boron nitride; the rest is the same as in Example 1.

[0038] Example 3 A scratch-resistant release film differs from Example 1 in that it contains 10 kg of polytetrafluoroethylene micro powder and 5 kg of organic surface-modified boron nitride; the rest of the contents are the same as in Example 1.

[0039] Example 4 A scratch-resistant release film differs from Example 1 in that it contains 6 kg of polytetrafluoroethylene micro powder and 9 kg of organic surface-modified boron nitride; the rest of the contents are the same as in Example 1.

[0040] Example 5 A scratch-resistant release film differs from Example 1 in that it contains 12 kg of polytetrafluoroethylene micro powder and 3 kg of organically surface-modified boron nitride; the rest of the contents are the same as in Example 1.

[0041] Example 6 A scratch-resistant release film differs from Example 1 in that: a styrene-butadiene block copolymer is used in place of a methyl methacrylate-butadiene-styrene copolymer by an equal mass; the rest is the same as in Example 1.

[0042] Example 7 A scratch-resistant release film differs from Example 1 in that it uses ethylene propylene diene monomer (EPDM) rubber in place of methyl methacrylate-butadiene-styrene copolymer; the rest is the same as in Example 1.

[0043] Example 8 A scratch-resistant release film differs from Example 1 in that the surface-modified boron nitride is derived from Preparation Example 3; the rest is the same as Example 1.

[0044] Example 9 A scratch-resistant release film differs from Example 1 in that the surface-modified boron nitride is derived from Preparation Example 4; the rest is the same as Example 1.

[0045] Example 10 A scratch-resistant release film differs from Example 1 in that the surface-modified boron nitride is derived from Preparation Example 5; the rest is the same as Example 1.

[0046] Example 11 A scratch-resistant release film differs from Example 1 in that the surface-modified boron nitride is derived from Preparation Example 6; the rest is the same as Example 1.

[0047] Example 12 A scratch-resistant release film differs from Example 1 in that an isocyanate crosslinking agent of equal mass is used instead of polymethylhydrosiloxane; the rest is the same as in Example 1.

[0048] Example 13 A scratch-resistant release film differs from Example 1 in that: methyltrimethoxysilane is used in place of polymethylhydrosiloxane by mass; the rest is the same as in Example 1.

[0049] Example 14 A scratch-resistant release film differs from Example 1 in that it uses dibutyltin dilaurate in place of the delayed platinum catalyst; the rest is the same as in Example 1.

[0050] Example 15 A scratch-resistant release film differs from Example 1 in that: the substrate layer is prepared from the following raw material components: 80 kg of PET resin, 5 kg of thermoplastic polyurethane, 1 kg of methyl methacrylate-butadiene-styrene copolymer, 0.1 kg of pentaerythritol ester antioxidant, and 1 kg of POE-g-MAH compatibilizer; the release coating is prepared from the following raw material components: 30 kg of silicone release agent, 6 kg of polytetrafluoroethylene micro powder, 4 kg of organic surface-modified boron nitride, 2 kg of polymethylhydrosiloxane, 0.1 kg of delayed platinum catalyst, 2 kg of ethoxylated polysilazane, 60 kg of ethyl acetate, and 20 kg of isopropanol; the remaining components are the same as in Example 1.

[0051] Example 16 A scratch-resistant release film differs from Example 1 in that: the substrate layer is prepared from the following raw material components: 95 kg of PET resin, 15 kg of thermoplastic polyurethane, 5 kg of methyl methacrylate-butadiene-styrene copolymer, 0.5 kg of pentaerythritol ester antioxidant, and 3 kg of POE-g-MAH compatibilizer; the release coating is prepared from the following raw material components: 50 kg of silicone release agent, 12 kg of polytetrafluoroethylene micro powder, 8 kg of organic surface-modified boron nitride, 5 kg of polymethylhydrosiloxane, 0.5 kg of delayed platinum catalyst, 5 kg of ethoxy polysilazane, 90 kg of ethyl acetate, and 30 kg of isopropanol; the remaining components are the same as in Example 1.

[0052] Examples 1-16 and Comparative Examples 1-2 were tested using the following methods: According to GB / T 6739-2022 "Determination of Hardness of Paints and Varnishes by Pencil Method", the pencil used was a high-grade drawing pencil of the Zhonghua brand, with hardness grades from softest to hardest: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H. Before use, the pencil lead was sanded smooth to form a flat cylindrical edge. The load was 7.35N, the scratch angle was 45°, the scratch speed was 0.5mm / s, and the scratch length was 10mm. For each hardness grade, at least three scratches were made at different locations on the sample. If the maximum depth of all three scratches was ≤5µm, the hardness grade was considered passed. The test started with the softest pencil and gradually increased the hardness until the critical hardness grade at which the coating was scratched was found. The hardness grade test results are shown in Table 1.

[0053] According to GB / T 6742-2007 "Paints and Varnishes - Bending Test (Cylindrical Shafts)", the release film coating is placed outwards and bent 180° against a series of cylindrical shafts of different diameters. The surface of the coating is checked for cracks, peeling, or other failures. The sample is 15mm wide and 100mm long, with a bending angle of 180°. Evaluation method: Start testing with the largest diameter shaft (Φ20mm). With the sample coating facing outwards, bend it 180° around the shaft. Under standard light, observe the coating in the bent area with a 10x magnifying glass. If there are no visible cracks or peeling, the test is considered passed. Repeat the test with smaller diameter shafts until the smallest shaft diameter that allows the sample to pass is found. A smaller shaft diameter indicates better flexibility. The smallest shaft diameter obtained is shown in Table 1.

[0054] Table 1. Test results of Examples 1-16 and Comparative Examples 1-2

[0055] Based on Table 1, Examples 1-16 and Comparative Examples 1-2 were analyzed, and the analysis is as follows: Compared with Example 1, the hardness grade of the release film in Example 1 is higher than that in Example 1. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Example 1 cracks or peels.

[0056] Compared to Comparative Example 1, Example 1 added ethoxy polysilazane; ethoxy polysilazane should form strong siloxane bonds to tightly connect the components in the coating together, forming an organic-inorganic hybrid network that makes the coating both wear-resistant and flexible; therefore, the addition of ethoxy polysilazane is necessary.

[0057] Compared with Example 1 and Comparative Example 2, the hardness grade of the release film in Example 1 is higher than that of the release film in Comparative Example 2. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Comparative Example 2 cracks or peels.

[0058] Compared to Comparative Example 2, the boron nitride added in Example 1 underwent organic surface modification treatment; after organic surface modification, the boron nitride can be uniformly dispersed in the organosilicon network, resisting scratches through physical barriers and stress dispersion; therefore, organic surface modification treatment of the added boron nitride is necessary.

[0059] Comparing Examples 1 and Examples 2-5, the hardness grade of the release film in Example 1 is higher than that in Examples 2-5, and the minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that in Examples 2-5; the hardness grade of the release film in Examples 2-3 is higher than that in Examples 4-5, and the minimum shaft diameter when the release film coating of Examples 2-3 cracks or peels is smaller than that in Examples 4-5.

[0060] Compared to Examples 4-5, the mass ratio of polytetrafluoroethylene (PTFE) micropowder to organic surface-modified boron nitride in Examples 1-3 is (1-2):1. PTFE micropowder reduces friction during scraping through lubrication, while boron nitride disperses stress through its high hardness and layered structure. At this ratio, both are uniformly dispersed in the organosilicon system. PTFE micropowder fills the gaps between boron nitride layers and synergistically forms a continuous protective layer, giving the coating both a low coefficient of friction and wear resistance. Therefore, a mass ratio of PTFE micropowder to organic surface-modified boron nitride of (1-2):1 is preferred.

[0061] Comparing Examples 1 and 6-7, the hardness grade of the release film in Example 1 is higher than that in Examples 6-7, and the minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Examples 6-7 cracks or peels.

[0062] Compared to Examples 6-7, the toughening agent in Example 1 is a methyl methacrylate-butadiene-styrene copolymer. The butadiene rubber core in the methyl methacrylate-butadiene-styrene copolymer is an elastomer, and the styrene-methyl methacrylate shell is compatible with PET resin. When subjected to external force, the methyl methacrylate-butadiene-styrene copolymer can absorb energy and prevent crack propagation, thereby improving the flexibility of the release film. Therefore, using methyl methacrylate-butadiene-styrene copolymer as the toughening agent is preferred.

[0063] Comparing Examples 1 and 8-9, the hardness grade of the release film in Example 1 is higher than that in Examples 8-9. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Examples 8-9 cracks or peels.

[0064] Compared to Examples 8-9, in Example 1, boron nitride was modified using a vinyl silane coupling agent. The vinyl functional groups of the vinyl-modified boron nitride participate in the hydrosilylation reaction of the organosilicon release agent, which enables the vinyl-modified boron nitride to be more firmly fixed in the coating and less likely to fall off, thereby improving the scratch resistance of the coating. Therefore, it is better to modify boron nitride using a vinyl silane coupling agent.

[0065] Comparing Example 1 and Examples 10-11, the hardness grade of the release film in Example 1 is higher than that in Examples 10-11. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Example 1 cracks or peels.

[0066] Compared to Examples 10-11, boron nitride in Example 1 was modified using a vinyltriethoxysilane coupling agent. The vinyltriethoxysilane coupling agent has a slower hydrolysis rate, which avoids the problem of uneven distribution of boron nitride in the coating. Therefore, it is better to modify boron nitride using a vinyltriethoxysilane coupling agent.

[0067] Comparing Examples 1 and 12-13, the hardness grade of the release film in Example 1 is higher than that in Examples 12-13. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Example 1 cracks or peels.

[0068] Compared to Examples 12-13, the crosslinking agent in Example 1 is polymethylhydrosiloxane. Polymethylhydrosiloxane is well compatible with other components in the release coating and undergoes hydrosilylation reaction with the silane bonds in the organosilicon release agent to form a crosslinked structure, which improves the hardness and wear resistance of the coating. Moreover, the crosslinked structure restricts the movement of molecular chains, reduces the plastic deformation of the coating during the scratching process, and enhances the scratch resistance of the coating. Therefore, polymethylhydrosiloxane is the preferred crosslinking agent.

[0069] Comparing Example 1 and Example 14, the hardness grade of the release film in Example 1 is higher than that in Example 14. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Example 1 cracks or peels.

[0070] Compared to Example 14, the catalyst in Example 1 is a delayed platinum catalyst; it has low activity at room temperature, but rapidly releases platinum active centers during high-temperature curing to catalyze the hydrosilylation reaction, making the reaction controllable and stable; therefore, a delayed platinum catalyst is preferred.

[0071] Comparing Example 1 and Examples 15-16, the hardness grade of the release film in Example 1 is higher than that in Examples 15-16. The minimum shaft diameter when the release film coating of Example 1 cracks or peels is smaller than that when the release film coating of Example 1 cracks or peels.

[0072] Compared to Examples 15-16, in Example 1, the mass ratio of PET resin, thermoplastic polyurethane, methyl methacrylate-butadiene-styrene copolymer, pentaerythritol ester antioxidant, and POE-g-MAH compatibilizer in the substrate layer was 90:10:3:0.3:2; and the mass ratio of silicone release agent, polytetrafluoroethylene micropowder, organic surface-modified boron nitride, polymethylhydrosiloxane, delayed platinum catalyst, ethoxylated polysilazane, ethyl acetate, and isopropanol in the release coating was 40:9:6:3:0.3:3:7. Therefore, the mass ratio of PET resin, thermoplastic polyurethane, methyl methacrylate-butadiene-styrene copolymer, pentaerythritol ester antioxidant, and POE-g-MAH compatibilizer in the substrate layer is 90:10:3:0.3:2; and the mass ratio of organosilicon release agent, polytetrafluoroethylene micro powder, organic surface-modified boron nitride, polymethylhydrosiloxane, delayed platinum catalyst, ethoxy polysilazane, ethyl acetate, and isopropanol in the release coating is 40:9:6:3:0.3:3:75:25, which is preferred.

[0073] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A scratch-resistant release film, characterized in that, It consists of a substrate layer and a release coating. The substrate layer comprises the following components in parts by weight: 80-95 parts of PET resin, 5-15 parts of thermoplastic polyurethane, 1-5 parts toughening agent Pentylenetetraethylene glycol ester antioxidant, 0.1~0.5 parts. 1-3 parts of POE-g-MAH compatibilizer; The release coating comprises the following components in parts by weight: 30-50 parts of silicone release agent 10-20 parts of wear-resistant additive, 2-5 parts of crosslinking agent Catalyst 0.1~0.5 parts, 2-5 parts of ethoxylated polysilazane Solvent 80-120 parts; The wear-resistant additives include polytetrafluoroethylene micro powder and organically surface-modified boron nitride. The solvent is a mixture of ethyl acetate and isopropanol.

2. The scratch-resistant release film according to claim 1, characterized in that, The mass ratio of the polytetrafluoroethylene micro powder to the organic surface-modified boron nitride is (1~2):

1.

3. The scratch-resistant release film according to claim 1, characterized in that, The toughening agent is a methyl methacrylate-butadiene-styrene copolymer.

4. The scratch-resistant release film according to claim 1, characterized in that, The organic surface-modified boron nitride is vinyl-modified boron nitride.

5. The scratch-resistant release film according to claim 4, characterized in that, The vinyl-modified boron nitride was obtained by modification with a vinyltriethoxysilane coupling agent.

6. The scratch-resistant release film according to claim 1, characterized in that, The crosslinking agent is polymethylhydrosiloxane.

7. The scratch-resistant release film according to claim 1, characterized in that, The catalyst is a delayed platinum catalyst.

8. A method for preparing a scratch-resistant release film according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: PET resin, thermoplastic polyurethane, toughening agent, pentaerythritol ester antioxidant, and POE-g-MAH compatibilizer are mixed to obtain a premix; the premix is ​​fed into a twin-screw extruder, extruded, cast into a film, stretched and shaped, and cooled to obtain a modified PET substrate. S2: Add organosilicon release agent, wear-resistant additive, crosslinking agent, catalyst, and ethoxy polysilazane to a mixed solvent, stir, disperse, and obtain release coating liquid; S3: Apply release coating liquid to one side of the modified PET substrate and cure the coated substrate.

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