Anti-aging aluminum foil grid composite film and production process thereof

Abstract

The invention relates to the field of high-performance composite materials, and discloses an anti-aging aluminum foil grid composite film and a production process thereof. 10 to 15 parts of a dynamic thiol cross-linking agent; 3-5 parts of a metal coordination cross-linking agent; 5-8 parts of a free radical trapping agent; 3-5 parts of an ultraviolet light absorber; 0.5 to 1 part of an organosilicon auxiliary agent; the aluminum foil layer is an aluminum foil with the purity being greater than or equal to 99.7%, and the thickness is 10-15 microns; the grid layer is a high-density polyethylene grid layer, and the hot melting bonding layer is a modified ethylene-vinyl acetate copolymer. Through aluminum foil anodic oxidation treatment, dynamic crosslinking coating design, grid layer surface modification and hot melting bonding layer enhancement, the aging resistance, interface bonding force and mechanical strength of the aluminum foil grid composite film in severe environments such as ultraviolet rays, high temperature and high humidity are remarkably improved, and long-term stability of barrier performance is achieved.

Description

Technical Field

[0001] The present invention relates to the field of high-performance composite materials, and particularly to an anti-aging aluminum foil grid composite film and its production process. Background Art

[0002] Aluminum foil grid composite films are widely used in packaging, construction, electronics and other fields due to their excellent barrier properties, mechanical strength and lightweight characteristics. However, these materials often need to be exposed to harsh environments such as ultraviolet light, high temperature and high humidity for a long time in practical applications, resulting in significant degradation of their performance and difficulty in meeting the requirements of high-end applications. In order to extend the service life of aluminum foil grid composite films, the existing technologies mainly improve the stability by improving the design of each functional layer, optimizing the interface bonding and enhancing the anti-aging performance. However, the existing improvement schemes still show obvious deficiencies in complex environments and are difficult to balance the performance stability and long-term reliability of each layer structure.

[0003] The existing aluminum foil grid composite films in the prior art include a multi-layer structure of an aluminum foil layer, a functional coating layer, a grid layer and a hot melt adhesive layer. The aluminum foil layer is mainly responsible for blocking external gases, moisture and ultraviolet light. However, the surface of the untreated aluminum foil is smooth and highly chemically inert, with insufficient bonding force with the functional coating layer, and it is easy to have interface delamination during the aging process, resulting in a rapid decline in the barrier performance. The functional coating layer delays aging by adding antioxidants or ultraviolet absorbers, but lacks dynamic repair ability, and the accumulation of free radical chain reactions will cause molecular chain breakage and coating cracking of the material. The grid layer mostly uses unmodified polymer materials, which are combined with the coating only by physical adsorption, resulting in poor interface bonding force and easy delamination under stress and aging conditions, affecting the overall mechanical properties of the composite film. The hot melt adhesive layer is easy to soften or degrade under high temperature and high humidity conditions, and it is difficult to maintain the interface bonding strength for a long time, and even causes interlayer detachment problems. These defects make it difficult for the composite films of the existing technologies to simultaneously meet the long-term requirements of barrier performance, anti-aging performance and mechanical strength, restricting their development in high-end application scenarios. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides an anti-aging aluminum foil grid composite film and its production process, which solves the problems of insufficient anti-aging performance, weak interlayer interface bonding force, and easy degradation of mechanical properties and barrier properties of aluminum foil grid composite films in harsh environments in the prior art.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: An anti-aging aluminum foil grid composite film, comprising the following components: 45 - 55 parts of polyurethane matrix; 10 - 15 parts of dynamic mercaptan crosslinking agent; 3 - 5 parts of metal coordination crosslinking agent; 5 - 8 parts of free radical scavenger; 3 - 5 parts of ultraviolet absorber; 0.5 - 1 part of silicone additive; The aluminum foil layer is made of aluminum foil with a purity ≥ 99.7%, and the thickness is 10 - 15 μm; the grid layer is a high - density polyethylene grid layer, and the hot - melt adhesive layer is a modified ethylene - vinyl acetate copolymer.

[0006] Preferably, the dynamic mercaptan cross - linker is 2,2'-dithiobisphenol or mercaptopropionic acid, and the metal coordination cross - linker is zinc acetate or iron acetylacetonate.

[0007] Preferably, the aluminum foil layer is anodized, and the surface roughness is 0.5 - 1.0 μm.

[0008] Preferably, the grid layer is surface - modified with a silane coupling agent, and the grid density is 5 - 10 grids / cm 2 , and the thickness is 80 - 120 μm.

[0009] Preferably, the thickness of the hot - melt adhesive layer is 5 - 10 μm, which contains 0.5 - 1 part of 2,2,6,6 - tetramethylpiperidine oxide and 1 - 2 parts of nano - silica particles.

[0010] A production process of an anti - aging aluminum foil grid composite film includes the following steps: Prepare a dynamic cross - linked functional coating, mix the polyurethane matrix and the dynamic mercaptan cross - linker in proportion, add a radical scavenger, an ultraviolet absorber and a metal coordination cross - linker, and stir evenly; Use a coater to coat the dynamic cross - linked functional coating on the surface of the aluminum foil, the coating thickness is 3 - 5 μm, the coating temperature is 50 - 70 °C, and cure after coating; Compound the aluminum foil layer and the grid layer with a hot - melt adhesive, the compounding temperature is 100 - 120 °C, and the pressure is 2 - 4 MPa; Carry out a curing treatment on the composite film, the curing temperature is 70 - 80 °C, and the time is 6 - 8 hours.

[0011] Preferably, the dynamic cross - linked functional coating is protected by nitrogen during the stirring process, the stirring time is 1 - 2 hours, and then degassing treatment is carried out under a pressure ≤ 100 Pa for 15 - 30 minutes.

[0012] Preferably, the coating curing time is 30 - 60 minutes, and the surface roughness of the cured coating is controlled at 0.1 - 0.2 μm.

[0013] Preferably, during the compounding process, a hot - melt adhesive modified with nano - silica particles and a silane coupling agent is used, and the compounding speed is 10 - 20 m / min.

[0014] Preferably, the post-treatment cooling step of the composite film is slow cooling under normal temperature conditions, and the cooling rate is 10-20 °C / h.

[0015] The present invention provides an anti-aging aluminum foil grid composite film and its production process. It has the following beneficial effects: 1. By adopting the combined design of a dynamic cross-linking functional coating and an aluminum foil layer, the present invention introduces a dynamic thiol-disulfide cross-linking network into the composite film. This structure can achieve self-healing ability through fracture and recombination under high temperature or photo-aging conditions. Compared with the design that simply relies on antioxidants in the prior art, the durability of the composite film under high temperature and ultraviolet environments is significantly improved, and the problem of performance decline caused by the expansion of microcracks in the material is solved.

[0016] 2. By introducing a radical scavenger and a metal coordination cross-linking agent into the dynamic cross-linking functional coating, the present invention constructs a synergistic anti-aging system. The radical scavenger effectively blocks the free radical chain reaction, and the metal coordination cross-linking enhances the high-temperature stability of the coating. Compared with the technology in the prior art that solely relies on ultraviolet absorbers to reduce photo-aging, the present invention solves the key problem of oxidation-induced aging and simultaneously extends the service life of the material.

[0017] 3. The present invention optimizes the structural design and process conditions of the aluminum foil layer. By combining high-purity aluminum foil with anodic oxidation treatment, excellent barrier performance and interfacial bonding strength are provided. In the prior art, the surface treatment of the aluminum foil layer is not fully considered, resulting in common problems of poor adhesion to the functional coating. The present invention significantly improves the overall structural stability of the composite film and overcomes the defects of interlayer separation and failure.

[0018] 4. By adding nano-silica particles and TEMPO radical stabilizers to the hot melt adhesive layer, the hot melt layer has both good adhesiveness and anti-aging ability. Compared with the defects of easy aging of ordinary hot melt adhesives and attenuation of bonding strength over time in the prior art, the present invention maintains excellent interlayer bonding strength in long-term high-humidity and high-temperature environments, thus meeting the application requirements of various complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0021] Please refer to the appendix Figure 1 , an embodiment of the present invention provides an anti-aging aluminum foil grid composite film, which includes an aluminum foil layer, a dynamic cross-linking functional coating, a grid layer, and a hot melt adhesive layer. The structures and material formulations of each layer are as follows: Aluminum foil layer (shielding layer) Material: High-purity aluminum foil with a purity ≥ 99.7% is selected, with a thickness of 10 - 15 μm, and an anodic oxidation treatment is carried out.

[0022] The aluminum foil layer serves as the first protection barrier of the composite film, playing a key role in blocking ultraviolet rays and oxygen. Ultraviolet rays can trigger photo-oxidation reactions in polymer materials, generating primary free radicals (R·). High-purity aluminum foil has excellent light reflection properties (ultraviolet reflectivity above 80%), which can effectively prevent ultraviolet rays from penetrating. At the same time, aluminum foil has excellent barrier properties, which can significantly reduce oxygen permeation and reduce the risk of free radical generation at the source. The anodic oxidation treatment further enhances the corrosion resistance of the aluminum foil surface and improves the bonding force with the dynamic cross-linking functional coating.

[0023] Dynamic cross-linking functional coating (repair layer) Composition and ratio (by mass): Polyurethane matrix: 45 - 55 Dynamic mercaptan cross-linking agent: 10 - 15 Metal coordination cross-linking agent: 3 - 5 Free radical scavenger: 5 - 8 Ultraviolet absorber: 3 - 5 Organosilicon auxiliary agent: 0.5 - 1 Repair function of the dynamic mercaptan cross-linking network: The coating introduces a dynamic mercaptan-disulfide bond (S-S bond) cross-linking agent, such as 2,2'-dithiobisphenol (DTBP). Under high temperature or photo-aging conditions, the S-S bond undergoes reversible cleavage to generate reactive mercapto groups (-SH). These mercapto groups regenerate S-S bonds through a dynamic recombination mechanism, thereby repairing molecular chain breaks and microcracks caused by stress or aging. This process is based on dynamic covalent chemical reactions (DCC), which can significantly improve the lifespan and structural stability of the material.

[0024] Free radical capture function: Hindered phenols (such as BHT) and phosphite esters (such as TPP) free radical scavengers are introduced into the coating to capture primary free radicals (R·) and secondary free radicals (ROO·). Among them, BHT neutralizes free radicals through a hydrogen atom transfer mechanism to form stable phenoxy free radicals, preventing the expansion of the free radical chain reaction; TPP further captures the oxidation product ROO·, enhancing the antioxidant effect.

[0025] Metal coordination cross-linking enhancement function: Add Zn ²⁺ or Fe ³⁺As a metal coordination crosslinking agent, it forms a reversible coordination bond crosslinking network. Under the action of external force or heat, the coordination bonds break to absorb energy, relieve the stress concentration of the material, and enhance the crosslinking stability in a high-temperature environment at the same time.

[0026] Ultraviolet absorption function: UV absorbers such as UV-531 are introduced into the coating, which can absorb ultraviolet light and convert it into heat energy for release, further reducing the generation of free radicals.

[0027] Humidity and heat resistance function: By adding silicone additives (such as polysiloxane derivatives), the humidity and heat resistance performance of the coating is improved to prevent moisture penetration and degradation under high humidity conditions.

[0028] Mesh layer (support layer) Material and parameters: Material: High-density polyethylene (HDPE), surface-treated with silane coupling agent.

[0029] Mesh density: 5 - 10 grids / cm², thickness is 80 - 120 μm.

[0030] The mesh layer mainly provides the mechanical strength and support structure of the composite film, preventing the material from tearing or deforming under stress. As a substrate, HDPE has good toughness and weather resistance and can stably exist in high humidity, high temperature, and oxygen environments for a long time. After modification of HDPE with silane coupling agent, chemical bonding can be formed between the mesh layer and the dynamic coating, improving the interfacial bonding strength.

[0031] Hot melt adhesive layer (interface layer) Material and parameters: Material: Modified ethylene-vinyl acetate copolymer (EVA).

[0032] Additives: TEMPO (0.51 parts) and nano-silica (12 parts).

[0033] Thickness: 5 - 10 μm.

[0034] The hot melt adhesive layer is responsible for connecting the aluminum foil layer and the mesh layer, enhancing the interlayer bonding strength of the overall composite film through chemical bonding and interfacial physical action. Nano-silica is dispersed in the interface, which can improve the mechanical properties of the interface and reduce the fluidity of the adhesive during thermal aging; the TEMPO free radical stabilizer further enhances the stability of the hot melt layer in a thermal oxygen environment, preventing delamination problems caused by aging.

[0035] Production process Preparation of the dynamic crosslinking functional coating Process steps: Under nitrogen protection, the polyurethane matrix and the dynamic thiol crosslinking agent are mixed in proportion (mass ratio 1:0.3:0.5), heated to 50-60 °C, and stirred for 1-2 hours to form a matrix solution.

[0036] The radical scavengers (BHT, TPP), ultraviolet absorber (UV-531), and metal complexing agent (Zn ²⁺ or Fe ³⁺ ) are added in sequence, and stirring is continued for 30-60 minutes to ensure uniform dispersion.

[0037] Finally, the silicone additive is added. After stirring evenly, degassing is carried out for 15-30 minutes in a vacuum environment (≤100 Pa).

[0038] The nitrogen protection environment can effectively avoid the coating oxidation reaction caused by oxygen during the stirring process; the vacuum degassing step can eliminate the microbubbles generated during the preparation process and ensure the uniformity and flatness of the coating.

[0039] Coating process Process steps: Use a high-precision coater to evenly coat the dynamic crosslinking functional coating on the surface of the aluminum foil layer.

[0040] The coating thickness is controlled at 3-5 μm, the coating temperature is 50-70 °C, and after coating, it is cured at 60-70 °C for 30-60 minutes.

[0041] The low-temperature coating and curing process effectively avoid the thermal oxidation of the polyurethane matrix at high temperatures and ensure the stable formation of the dynamic crosslinking network structure.

[0042] Lamination of aluminum foil and grid layer Process steps: Laminating the aluminum foil coated with the dynamic crosslinking functional coating and the grid layer with a hot melt adhesive.

[0043] Lamination conditions: temperature 100-120 °C, pressure 2-4 MPa, lamination speed 10-20 m / min.

[0044] During the lamination process, a bonding layer with higher interfacial bonding strength is formed through the dispersion of nano-silica, and at the same time, the hot melt process effectively avoids the interfacial damage between layers caused by excessive temperature.

[0045] Post-treatment Process steps: After the composite film is completed, it is placed in a constant temperature furnace at 70-80 °C for curing for 6-8 hours.

[0046] Slowly cool at room temperature, and the cooling rate is controlled at 10-20 °C / h.

[0047] The slow cooling process can effectively release the thermal stress between the film layers and prevent warping or interfacial microcracks caused by rapid cooling. Example

[0048] Preparation of Aluminum Foil Mesh Composite Film Preparation of Aluminum Foil Layer Select high-purity aluminum foil with a purity of 99.7% and control the thickness at 12 μm. Treat the surface of the aluminum foil through an anodizing process. Use sulfuric acid solution as the electrolyte, control the treatment temperature at 15°C, voltage at 20 V, and time at 10 minutes. After oxidation, wash with deionized water and dry, set the temperature at 70°C and time at 30 minutes. After treatment, the surface roughness of the aluminum foil is about 0.8 μm.

[0049] Preparation of Dynamically Crosslinked Functional Coating Add 45 parts of polyurethane matrix, 12 parts of dynamic thiol crosslinking agent (2,2'-dithiobisphenol), and 4 parts of zinc acetate solution (mass concentration 10%) according to the ratio. Control the stirring temperature at 50°C and time at 1.5 hours. Then add 3 parts of BHT, 2 parts of TPP, and 3 parts of UV-531, and continue stirring for 40 minutes. Finally, add 0.8 part of silicone additive and defoam under vacuum conditions for 20 minutes to complete the coating preparation.

[0050] Coating Evenly coat the above coating solution on the surface of the aluminum foil. Use a coater to control the coating thickness at 4 μm and the coating speed at 30 m / min. After coating, place it in a curing furnace at a temperature of 65°C for 40 minutes to cure the coating.

[0051] Lamination After the high-density polyethylene (HDPE) mesh layer is modified with a silane coupling agent, laminate it onto the aluminum foil layer. Use modified EVA as the hot melt adhesive, and add 1% TEMPO and 1.5% nano-silica particles. Set the lamination temperature at 110°C, pressure at 3 MPa, and lamination speed at 15 m / min.

[0052] Post-treatment Cure the composite film at 70°C for 6 hours, and cut it into standard-size samples after cooling to room temperature. Example

[0053] Optimized Preparation of Dynamically Crosslinked Coating Coating Formulation Add 50 parts of polyurethane prepolymer and 10 parts of mercaptopropionic acid to a stirring kettle in proportion, and stir for 2 hours at 60 °C. Subsequently, add 3.5 parts of iron acetylacetonate solution (mass concentration 8%), and continue stirring for 30 minutes. Add 4 parts of BHT, 3 parts of UV-531 and 2 parts of TPP. After mixing evenly, add 0.7 part of polysiloxane auxiliary agent. After stirring, degas the coating liquid under a vacuum condition of 100 Pa for 15 minutes to form a uniform coating solution.

[0054] Coating and Curing The coating machine evenly coats the above coating liquid on the surface of an aluminum foil with a thickness of 10 μm. The coating thickness is 3 μm, and the coating speed is 40 m / min. After coating, the sample is placed in a curing box, the curing temperature is set at 60 °C, and the time is 30 minutes to complete the curing of the coating.

[0055] Lamination Step Compound the aluminum foil treated with the coating with an HDPE mesh layer with a mesh density of 8 grids / cm². The hot melt adhesive is modified EVA, and 1.2% nano-silica and 0.8% TEMPO are added. The lamination temperature is 105 °C, the pressure is 2.5 MPa, and the speed is 12 m / min.

[0056] Post-treatment The curing temperature is 70 °C and the time is 7 hours. During the cooling process, control the cooling speed to be 15 °C / h, and finally complete the preparation of the aging-resistant composite film. Example

[0057] Preparation of Reinforced Aluminum Foil Composite Film Aluminum Foil Treatment Select an aluminum foil with a thickness of 15 μm and carry out anodic oxidation treatment. The anodic oxidation solution is phosphoric acid solution, the voltage is 25 V, and the treatment time is 15 minutes. After oxidation, rinse with deionized water and dry at 60 °C for 30 minutes.

[0058] Functional Coating Preparation Prepare the coating liquid, add 47 parts of polyurethane matrix, 13 parts of 2,2'-dithiobisphenol and 4 parts of zinc acetate, and stir for 1.5 hours. Subsequently, add 3.5 parts of BHT, 2.5 parts of TPP and 3 parts of UV-531, and continue stirring for 50 minutes. Finally, add 0.6 part of silicone auxiliary agent. After stirring evenly, degas under vacuum conditions for 15 minutes.

[0059] Coating and Curing The coating liquid is coated on the surface of the aluminum foil with a thickness of 4 μm, the coating temperature is 55 °C, and the coating speed is 25 m / min. After coating, the curing conditions are 65 °C and the time is 40 minutes.

[0060] Lamination Step The thickness of the HDPE mesh layer is controlled at 100μm, and the mesh density is 6 grids / cm². EVA hot melt adhesive is used, in which 2% nano-silicon dioxide particles and 1% TEMPO are added. The composite process parameters are: temperature 120℃, pressure 3MPa, speed 10m / min.

[0061] Curing and cooling The composite film was cured at 70°C for 6 hours and then cooled to room temperature at a rate of 10°C / h to complete the sample preparation. Example

[0062] Preparation of high-strength composite membrane Aluminum foil treatment A high-purity aluminum foil with a purity of 99.9% and a thickness of 14μm was used. After chemical etching, the aluminum foil was further anodized with a mixed acid solution (sulfuric acid-phosphoric acid) at a temperature of 20°C for 8 minutes. The thickness of the oxide layer was about 1μm.

[0063] Functional coating According to the ratio, add 50 parts of polyurethane matrix, 10 parts of dynamic thiol crosslinker (mercaptopropionic acid), 3.8 parts of ferric acetylacetonate solution, 3 parts of BHT, 2.5 parts of TPP, 3.2 parts of UV-531 and 0.5 parts of silicone additive. Stir for 1.5 hours and vacuum degas for 20 minutes.

[0064] Coating and curing The coating liquid was evenly coated on the surface of the aluminum foil with a thickness of 5 μm and a coating speed of 30 m / min. The curing conditions after coating were 65° C. and the time was 35 minutes.

[0065] complex Aluminum foil is compounded with HDPE mesh treated with silane coupling agent, with a mesh layer thickness of 120μm and a density of 7 grids / cm². 1% TEMPO and 1.8% nano-silica are added to the hot melt adhesive. The compounding temperature is 115℃, the pressure is 3MPa, and the speed is 15m / min. After the compounding is completed, it is cured at 70℃ for 8 hours and cooled to room temperature to complete the preparation. Example

[0066] Optimized preparation process of composite membrane Aluminum foil and coating treatment The thickness of the aluminum foil is 10 μm, and the surface roughness after anodizing is 0.6 μm. The functional coating is prepared using 48 parts of polyurethane matrix, 12 parts of 2,2'-disulfide bisphenol, 4.2 parts of zinc acetate, 3 parts of BHT, 2 parts of TPP and 3 parts of UV-531, with a stirring time of 2 hours and a degassing time of 15 minutes.

[0067] Coating and curing Coating thickness is 3 μm, coating speed is 20 m / min, curing temperature after coating is 60 °C, and time is 40 minutes.

[0068] Lamination step The grid layer uses HDPE, the grid density is 9 grids / cm², and the thickness is 90 μm. 1.5% nano-silica and 0.8% TEMPO are added to the hot melt adhesive layer. The lamination temperature is 120 °C, the pressure is 2.8 MPa, and the lamination speed is 18 m / min.

[0069] Post-treatment Curing temperature is 70 °C, time is 7 hours, and the cooling rate is 12 °C / h to complete the preparation of the final composite film.

[0070] Comparative Example 1 Differences from Example 1 In this comparative example, a dynamic thiol crosslinking agent was not introduced into the dynamic crosslinking functional coating, and only a polyurethane matrix and an antioxidant were used to prepare the coating.

[0071] Preparation process Dynamic functional coating Only 50 parts of polyurethane matrix, 3 parts of BHT, 2 parts of TPP, 3 parts of UV-531, and 0.5 part of silicone additive were added to the formulation. A dynamic thiol crosslinking agent (2,2'-dithiobisphenol) and a metal coordination crosslinking agent (zinc acetate) were not added. After mixing, it was stirred for 1 hour and degassed under vacuum for 15 minutes to complete the preparation of the coating liquid.

[0072] Coating and curing Coating thickness is 4 μm, coating speed is 30 m / min, curing temperature after coating is 65 °C, and curing time is 40 minutes.

[0073] Lamination step The process parameters of the laminated grid layer remain the same. 1% TEMPO and 1.5% nano-silica are added to the hot melt adhesive layer. The lamination temperature is 110 °C, the pressure is 3 MPa, and the speed is 15 m / min.

[0074] Comparative Example 2 Differences from Example 2 In this comparative example, radical scavengers (BHT, TPP) were not introduced into the dynamic crosslinking functional coating, and only anti-aging performance was provided by a dynamic thiol crosslinking agent and a metal coordination crosslinking agent.

[0075] Preparation process Dynamic functional coating The formulation includes 50 parts of polyurethane matrix, 12 parts of mercaptopropionic acid, 3.5 parts of iron acetylacetonate solution, 3 parts of UV-531 and 0.7 part of silicone additive. Free radical scavengers (BHT, TPP) are not added. The stirring temperature is controlled at 60°C for 2 hours, followed by vacuum degassing for 20 minutes.

[0076] Coating and curing The coating thickness is controlled at 3 μm, the coating temperature is 55°C, and the coating speed is 40 m / min. After coating, it is cured at 60°C for 30 minutes.

[0077] Lamination step The lamination step is the same as that in Example 2, using a modified EVA hot melt adhesive layer. The lamination temperature is 105°C, the pressure is 2.5 MPa, and the speed is 12 m / min.

[0078] Comparative Example 3 Differences from Example 3 In this comparative example, the grid layer was not treated with a silane coupling agent, and the untreated HDPE grid layer was directly used.

[0079] Preparation process Aluminum foil treatment The treatment steps of the aluminum foil layer are the same as those in Example 3.

[0080] Dynamic functional coating The formulation of the dynamic coating is the same as that in Example 3.

[0081] Lamination step The grid layer uses untreated HDPE material with a thickness of 100 μm and a grid density of 6 grids / cm². The lamination temperature is 120°C, the pressure is 3 MPa, and the lamination speed is 10 m / min.

[0082] Post-treatment The curing step remains unchanged, with a curing temperature of 70°C and a time of 6 hours.

[0083] Comparative Example 4 Differences from Example 4 In this comparative example, TEMPO and nano-silica were not added to the hot melt adhesive layer, and only ordinary EVA hot melt adhesive was used.

[0084] Preparation process Aluminum foil treatment and coating preparation The preparation processes of the aluminum foil layer and the dynamic coating are both the same as those in Example 4.

[0085] Lamination step The hot-melt adhesive layer does not contain 1% TEMPO and 1.8% nano-silica, and only modified EVA is used as the adhesive. The lamination temperature is 115 °C, the pressure is 3 MPa, and the lamination speed is 15 m / min.

[0086] Post-treatment The curing and cooling conditions are kept consistent, the curing temperature is 70 °C, and the time is 8 hours.

[0087] Comparative Example 5 Differences from Example 5 In this comparative example, the aluminum foil layer is not anodized, and the untreated aluminum foil is directly used as the barrier layer.

[0088] Preparation process Aluminum foil layer Ordinary aluminum foil with a thickness of 10 μm is selected, and the surface is not anodized.

[0089] Dynamic functional coating The formulation of the dynamic functional coating is the same as that in Example 5.

[0090] Coating and curing The coating thickness is 3 μm, the coating speed is 20 m / min, the curing temperature after coating is 60 °C, and the curing time is 40 minutes.

[0091] Lamination step The preparation processes of the mesh layer and the hot-melt adhesive layer are the same as those in Example 5. The lamination temperature is 120 °C, the pressure is 2.8 MPa, and the lamination speed is 18 m / min.

[0092] Post-treatment The post-treatment conditions remain unchanged, the curing temperature is 70 °C, the time is 7 hours, and the cooling rate is 12 °C / h.

[0093] Experiment 1: Verification of the self-healing performance of the dynamic crosslinked coating Experimental procedure Sample preparation Prepare the aluminum foil coating samples in Example 1 and Comparative Example 1, and cut them into 50 mm × 50 mm specifications. After the samples are prepared, perform surface cleaning treatment, wipe with lint-free cloth and anhydrous ethanol to remove surface impurities. The number of samples in each group is 3 pieces for repeated experiments.

[0094] Artificial scratch test Use a scratch tester to create scratches with a depth of about 20 μm on the sample surface. The scratch width is set to 1 mm and the length is 30 mm. During the scratch generation process, keep the load constant to ensure uniform scratch morphology. After scratching, observe and confirm the depth and width with a microscope.

[0095] Repair test The scratched samples were placed in an incubator at 60°C and left standing for 12 hours. During the repair process, the constant temperature environment was maintained, and the surface of the samples was not affected by external forces.

[0096] Scratch depth measurement A laser measuring instrument was used to measure the depth change after scratch repair, and the initial scratch depth and the depth after repair were recorded separately. Depth data at multiple positions (≥5 points) were taken for each sample, and the average value was calculated.

[0097] Calculation of repair rate The repair rate was calculated according to the formula: Repair rate = (Initial scratch depth - Scratch depth after repair) / Initial scratch depth × 100%.

[0098] Experimental data Table name: Sample type Initial scratch depth (μm) Depth 1 after repair (μm) Depth 2 after repair (μm) Depth 3 after repair (μm) Average depth after repair (μm) Repair rate (%) Example 1-1 20.1 3.8 4.5 4.2 4.17 79.3 Example 1-2 19.8 4 4.8 4.1 4.3 78.3 Example 1-3 20.3 3.9 4.6 4.4 4.3 78.8 Comparative example 1-1 20 16.5 16.1 15.8 16.13 19.4 Comparative example 1-2 19.7 15.8 16.4 16.2 16.13 18.1 Comparative example 1-3 20.2 16.2 16.6 15.9 16.23 19.7 Through the self - repair performance test of the dynamic cross - linked functional coating in this experiment, the core role of the thiol - disulfide dynamic cross - linked network was clearly revealed. In Example 1, the scratch depth was significantly reduced, and the repair rate was over 78%, fully verifying the reaction mechanism of dynamic fracture and recombination of thiol groups. The dynamic characteristics of this molecular network can be rapidly rebuilt after damage, indicating that the coating has excellent self - healing ability. In Comparative Example 1, due to the absence of a dynamic thiol cross - linker, the scratch depth only decreased slightly, mainly relying on the microscopic creep process of the material body, and the repair rate was less than 20%, lacking a dynamic repair mechanism.

[0099] The dynamic thiol cross - linker provides flexible molecular cross - linking points in the coating. When a scratch is formed, the thiol - disulfide bonds break first to absorb local stress, and in a constant temperature environment, active thiol groups regenerate cross - links through thermal - induced reactions, thus completing the closure of micro - damages. In contrast, the coating structure in Comparative Example 1 completely relies on the fixed cross - linked network of the polyurethane matrix, lacking dynamic reaction ability, difficult to repair damage accumulation, and long - term existence of surface defects, affecting the overall performance of the material.

[0100] The results of this experiment also show that the formation of the dynamic cross - linked network not only improves the damage resistance of the coating but also provides the possibility for long - life design in complex application environments. The advantage of this dynamic repair is especially suitable for fields that need to deal with scratches, abrasions, and impacts, further demonstrating the unique value of the technical solution of the present invention in practical applications.

[0101] Experiment 2: Verification of free - radical capture performance Experimental procedures Sample preparation The aluminum foil composite film samples prepared in Example 2 and Comparative Example 2 were selected and cut into a size of 100 mm × 100 mm. The samples were placed with the front side facing outwards, cleaned with absolute ethanol, and left standing to dry.

[0102] UV aging test Use a UV aging test chamber with a UV-A lamp as the light source, a wavelength of 340 nm, a light intensity of 40 W / m², and the test temperature set at 60 °C. Place the sample horizontally, with a test time of 500 hours. Regularly check whether the sample remains intact to avoid damage during the experiment.

[0103] Performance detection After aging, measure the tensile strength and oxygen transmission rate of the sample: Tensile strength: Use an electronic tensile testing machine for testing. The clamping distance of the sample is 50 mm, and the tensile speed is 10 mm / min. Record the maximum tensile force (N).

[0104] Oxygen transmission rate: Use an oxygen transmission rate tester. Set the test temperature at 23 °C and the relative humidity at 50%. Measure the oxygen transmission rate of the sample in units of cm³ / m²·day·atm.

[0105] Data recording Each group of samples is tested 3 times, and the average value is taken as the result. Compare the differences in tensile strength and oxygen permeability performance between the samples of Example 2 and Comparative Example 2, and analyze the effect of the radical scavenger.

[0106] Experimental data Table name: Sample type Tensile strength 1 (N) Tensile strength 2 (N) Tensile strength 3 (N) Average tensile strength (N) Oxygen transmission rate 1 (cm³ / m²·day·atm) Oxygen transmission rate 2 (cm³ / m²·day·atm) Oxygen transmission rate 3 (cm³ / m²·day·atm) Average oxygen transmission rate (cm³ / m²·day·atm) Example 2-1 35.6 36.4 34.9 35.63 1.02 1.08 1.04 1.05 Example 2-2 35.1 36 34.8 35.3 1.07 1.1 1.05 1.07 Example 2-3 35.3 36.2 35 35.5 1.03 1.06 1.04 1.04 Comparative example 2-1 23.2 22.8 23.5 23.17 2.67 2.78 2.69 2.71 Comparative example 2-2 22.9 22.6 23.3 22.93 2.62 2.75 2.68 2.68 Comparative example 2-3 23.1 22.7 23.4 23.07 2.7 2.72 2.66 2.69 The experiment clearly demonstrates the contribution of the radical scavenger to the anti-aging performance. The tensile strength of the sample in Example 2 remains above 35 N after UV aging, and the oxygen transmission rate is controlled at about 1.05, showing excellent mechanical strength and barrier properties. This is closely related to the introduction of BHT and TPP in the coating. BHT effectively terminates the chain radical reaction by providing stable phenoxy radicals, while TPP further captures peroxide radicals (ROO·). The dual protection mechanism greatly slows down the coating degradation caused by photooxidation. Due to the lack of a radical scavenger, the tensile strength of the sample in Comparative Example 2 decreases significantly, and the oxygen transmission rate increases to more than 2.7, with the anti-aging effect far inferior to that of the example.

[0107] During the UV aging process, the generation of radicals is the key driving force for polymer degradation. The significant performance advantages of the sample in Example 2 are due to the synergistic effect of the radical scavenger. BHT plays a role at the initial stage of radical generation induced by UV radiation and prevents the expansion of the chain reaction through hydrogen atom transfer; at the same time, TPP further captures secondary radicals, reducing the accumulation of oxidative damage. In Comparative Example 2, due to the lack of these two key components, radicals accumulate rapidly, resulting in the breakage of the molecular chain and the instability of the structure of the material, and a significant reduction in mechanical strength, showing obvious aging deterioration.

[0108] As can be seen from the results, the free radical capture system of Example 2 not only protects the structural integrity of the material in a photo-oxidation environment, but also significantly improves the retention ability of the barrier performance. This performance advantage is particularly crucial for application scenarios that require long-term exposure to light, high temperature, and oxygen, such as food packaging, outdoor building materials, etc., demonstrating the core competitiveness of the technology of the present invention.

[0109] Experiment 3: Influence of the surface modification of the grid layer on the interfacial bonding strength Experimental procedure Sample preparation Select the aluminum foil grid composite film samples prepared in Example 3 and Comparative Example 3, and cut them into specifications of 50 mm × 200 mm. The surface of the samples is cleaned with anhydrous ethanol and left to dry naturally. Ensure that the samples are undamaged and uncontaminated.

[0110] Peel strength test Use a 180° peel tester for testing. Fix the aluminum foil layer of the sample on the upper fixture and the grid layer on the lower fixture. The test speed is set to 50 mm / min, and the clamping distance is 30 mm. Record the peel force (N) required during the peeling process, and record the data in real time through a mechanical sensor. Each group of samples is tested 5 times.

[0111] Data processing According to the test curve, calculate the average peel strength (unit: N / cm). The peel strength formula is: Peel strength = Peel force / Sample width.

[0112] Experimental setup The test environment temperature is controlled at 23 °C and the relative humidity is 50%.

[0113] Each sample is tested repeatedly to ensure the accuracy of the data.

[0114] Experimental data Table name: Sample type Peeling force 1 (N) Peeling force 2 (N) Peeling force 3 (N) Peeling force 4 (N) Peeling force 5 (N) Average peeling force (N) Average peeling strength (N / cm) Example 3-1 4.8 5.2 5 4.7 5.3 5 10 Example 3-2 5.1 4.9 5.3 5 5.2 5.1 10.2 Example 3-3 5.2 4.8 5.1 5 5.4 5.1 10.2 Comparative example 3-1 2.6 2.8 2.7 2.5 2.9 2.7 5.4 Comparative example 3-2 2.7 2.9 2.8 2.6 2.8 2.76 5.5 Comparative example 3-3 2.8 2.7 2.6 2.9 2.5 2.7 5.4 The experimental results clearly show a significant improvement in the interfacial bonding strength due to the surface modification of the grid layer with silane coupling agent. The average peel strength of Example 3 reaches 10 N / cm, much higher than 5.4 N / cm of Comparative Example 3. The chemical activity of the silane coupling agent forms reactive sites on the surface of the grid layer, which bind to the functional groups in the coating through chemical bonds. This chemical bonding significantly enhances the interlayer bonding strength. In Comparative Example 3, the untreated grid layer and the coating are mainly combined through physical adsorption, resulting in a low interfacial bonding strength, poor force stability during the peeling process, and a low peel strength.

[0115] Mechanistically, the function of silane coupling agents is not limited to improving surface wettability. They can also provide stable interfacial bonding through their bifunctional structure. During the coating composite process, one end of the coupling agent reacts with the polymer chains of the grid layer to form chemical bonds, and the other end binds to the dynamic coating through hydrogen bonds or covalent bonds. This two-way interaction significantly reduces interfacial defects and further enhances the overall structural stability of the composite film. In Comparative Example 3, there are no reactive sites on the surface of the grid layer, resulting in the easy generation of microvoids at the interface. These defects are rapidly amplified during the peeling process, leading to a decrease in the bonding strength.

[0116] It is worth mentioning that the significant improvement in the interfacial bonding strength in Example 3 is particularly suitable for application scenarios that require high mechanical strength and durability, such as building insulation materials and high-end packaging fields. The strong bonding between the coating and the grid layer not only enables the composite film to better withstand the peeling force but also enhances the tear resistance, demonstrating the practical application potential and core competitiveness of the technical solution of the present invention.

[0117] Experiment 4: Verification of the enhanced effect of the hot melt adhesive layer Experimental procedures Sample preparation Prepare the composite film samples in Example 4 and Comparative Example 4, and cut them into 100 mm × 100 mm sizes. Ensure that the edges of the samples are free of burrs, clean the surfaces with anhydrous ethanol, and dry them for later use.

[0118] Accelerated aging test Place the samples in a thermo-hygrostat chamber, set the test environment to 85°C and 85% relative humidity, and the aging time to 500 hours. During the aging process, check the appearance of the samples every 100 hours to confirm that there are no obvious damages such as blistering or delamination.

[0119] Performance testing After the aging test, conduct the following two tests on the samples: Peel strength test: Use a 180° peel tester to test the interfacial peel strength between the aluminum foil layer and the grid layer. The peel speed is 50 mm / min, and the clamping distance is 30 mm. Record the peel force (N) and calculate the peel strength (N / cm).

[0120] Microscopic cross-section observation: Use a scanning electron microscope (SEM) to observe the interlayer interface of the samples and record whether there are delamination, voids, or cracks.

[0121] Data recording Each group of samples is tested 5 times, and the average value is taken as the peel strength result.

[0122] The microscopic observation results are recorded as a text description and analyzed in combination with the images.

[0123] Experimental data Table Name: Sample type Peeling force 1 (N) Peeling force 2 (N) Peeling force 3 (N) Peeling force 4 (N) Peeling force 5 (N) Average peeling force (N) Average peeling strength (N / cm) Example 4-1 6.8 7.2 7 6.9 7.3 7.04 14.1 Example 4-2 6.9 7.1 6.8 7.4 7 7.04 14.1 Example 4-3 7 7.3 7.1 7.2 6.9 7.1 14.2 Comparative example 4-1 3.2 3.5 3.6 3.4 3.1 3.36 6.7 Comparative example 4-2 3.4 3.3 3.5 3.6 3.2 3.4 6.8 Comparative example 4-3 3.3 3.2 3.4 3.6 3.5 3.4 6.8 The experimental results clearly demonstrate the significant effect of the hot-melt adhesive layer enhancement formulation in Example 4. The hot-melt adhesive layer containing nano-silica and TEMPO enables the sample of Example 4 to maintain a peel strength as high as 14 N / cm after accelerated aging, while the peel strength of the sample of Comparative Example 4 is only 6.7 N / cm. Microscopic observation shows that there are obvious microvoids and cracks at the bonding interface in Comparative Example 4, while the interface structure in Example 4 is dense without delamination. This difference is closely related to the functional enhancement of the hot-melt layer.

[0124] In Example 4, the high specific surface area of nano-silica forms physical crosslinking points in the adhesive layer, significantly enhancing the mechanical properties of the interlayer interface. And TEMPO, as a free radical stabilizer, effectively inhibits the oxidative degradation reaction under high temperature and high humidity environments. This synergistic effect not only improves the bonding strength between layers but also delays the decline of interface performance during the aging process. In contrast, these functional components are missing in Comparative Example 4, and the adhesive layer gradually softens and even delaminates during aging, resulting in a significant decrease in peel strength.

[0125] Mechanistically, the enhancement formulation of the hot-melt layer does not achieve performance improvement solely through physical filling. Nano-silica improves the interfacial bonding force through chemical interactions with the adhesive matrix and further slows down the fluidity of the adhesive under high temperature conditions. The introduction of TEMPO plays a key role in blocking the free radical chain reaction in the thermal oxygen environment. These combined effects jointly endow Example 4 with excellent aging resistance and interface stability.

[0126] Generally speaking, the technical solution of Example 4 is particularly suitable for material application scenarios that need to withstand high temperature and high humidity environments for a long time, such as food packaging and outdoor building materials. This technical advantage is not only reflected in the maintenance of the interlayer bonding force but also significantly improves the overall durability of the composite film, fully demonstrating the originality and superiority of the present invention in the design of the hot-melt adhesive layer.

[0127] Experiment 5: Influence of Aluminum Foil Surface Treatment on Barrier Performance Experimental Procedures Sample Preparation Select the composite film samples of Example 5 and Comparative Example 5, and cut them into specifications of 100 mm × 100 mm. Ensure that the sample edges are neat and there are no obvious damages. After wiping the aluminum foil surface with anhydrous ethanol, let it dry naturally.

[0128] Oxygen Transmission Rate Test Place the sample in an oxygen transmission rate tester. The test temperature is 23°C and the relative humidity is 50%. The test time is 24 hours. Record the oxygen transmission rate of the sample (unit: cm³ / m²·day·atm). Each group of samples is tested 3 times and the average value is taken.

[0129] Interface Observation Use a scanning electron microscope (SEM) to perform a cross-sectional observation on the interface between the aluminum foil layer and the dynamic cross-linked coating, and record whether there are obvious delamination, pores or interface roughness differences.

[0130] Experimental Setup The test conditions are strictly kept constant to avoid the influence of environmental fluctuations on the results.

[0131] Each group of samples is tested repeatedly to ensure data accuracy.

[0132] Experimental Data Table Name: Sample type Oxygen transmission rate 1 (cm³ / m²·day·atm) Oxygen transmission rate 2 (cm³ / m²·day·atm) Oxygen transmission rate 3 (cm³ / m²·day·atm) Average oxygen transmission rate (cm³ / m²·day·atm) Interface observation description Example 5-1 0.98 1.02 1.01 1 The interface is flat and well combined Example 5-2 1.03 1.01 0.97 1 There are no voids and the surface roughness is uniform Example 5-3 1.02 0.96 1 0.99 The interlayer combination is good and there is no delamination Comparative example 5-1 3.45 3.6 3.52 3.52 The interface is rough and the delamination is obvious Comparative example 5-2 3.41 3.55 3.5 3.49 There are micropores and the interlayer combination is poor Comparative example 5-3 3.46 3.47 3.49 3.47 The interface is uneven and there are microcracks The experimental data clearly show a significant improvement in the barrier performance due to the anodic oxidation treatment of the aluminum foil. The average oxygen transmission rate of Example 5 is only 1.00 cm³ / m²·day·atm, which is much lower than 3.49 cm³ / m²·day·atm of Comparative Example 5, demonstrating excellent oxygen barrier effect. The scanning electron microscope observation reveals that the interface of Example 5 is flat and dense, without obvious delamination and pores, and the interface is tightly bonded. This is directly related to the dense oxide film formed by the anodic oxidation treatment of the aluminum foil layer, which not only improves the surface roughness of the aluminum foil, but also significantly enhances the adhesion of the dynamic coating and the interface bonding quality. In Comparative Example 5, due to the lack of anodic oxidation treatment, the surface of the aluminum foil is rough and uneven, resulting in weak interlayer bonding force, and the presence of micropores and voids seriously reduces the barrier performance.

[0133] Mechanistically, the main role of the anodic oxidation treatment is to generate a stable and dense oxide layer on the surface of the aluminum foil through an electrochemical reaction. The formation of the oxide layer not only enhances the antioxidant performance of the aluminum foil, but also increases the contact area between the coating and the aluminum foil through the refined microstructure. This enhanced interface bonding reduces the formation of interface micropores and significantly improves the barrier performance of the overall composite film. In contrast, in Comparative Example 5, the surface of the aluminum foil is untreated, and the interface bonding completely depends on the physical adhesion of the coating, with significant micro-defects, resulting in a significant increase in the oxygen transmission rate.

[0134] The experiment also reveals that the improvement of the anodic oxidation treatment on the interfacial bonding is not only reflected in the static performance, but also provides guarantee for the long-term use of the composite film. The tightly bonded interface can reduce the erosion of the material performance by the external environment (moisture, oxygen), thereby enhancing the stability and lifespan of the material. The technical solution of Example 5 is particularly suitable for promotion and application in fields with high barrier requirements, such as pharmaceutical packaging, food preservation and other scenarios, further highlighting the innovative value and practical potential of the present invention in material design.

[0135] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An aging-resistant aluminum foil grid composite film, characterized in that: It includes the following components: 45-55 parts of polyurethane matrix; 10-15 parts of dynamic thiol crosslinking agent; 3-5 parts of metal coordination cross-linking agent; 5-8 parts of free radical scavenger; 3-5 parts of ultraviolet absorber; 0.5-1 part of silicone additive; The aluminum foil layer is an aluminum foil with a purity of ≥99.7% and a thickness of 10-15 μm; the mesh layer is a high-density polyethylene mesh layer, and the hot-melt adhesive layer is a modified ethylene-vinyl acetate copolymer.

2. The aging-resistant aluminum foil grid composite film according to claim 1, characterized in that: The dynamic thiol crosslinking agent is 2,2'-disulfide bisphenol or mercaptopropionic acid, and the metal coordination crosslinking agent is zinc acetate or ferric acetylacetonate.

3. The aging-resistant aluminum foil grid composite film according to claim 1, characterized in that: The aluminum foil layer is anodized and has a surface roughness of 0.5 to 1.0 μm.

4. The aging-resistant aluminum foil grid composite film according to claim 1, characterized in that: The mesh layer is surface-modified by a silane coupling agent, and has a mesh density of 5 to 10 grids / cm² and a thickness of 80 to 120 μm.

5. The aging-resistant aluminum foil grid composite film according to claim 1, characterized in that: The hot-melt adhesive layer has a thickness of 5 to 10 μm and contains 0.5 to 1 part of 2,2,6,6-tetramethylpiperidinyl oxide and 1 to 2 parts of nano silicon dioxide particles.

6. A production process for an aging-resistant aluminum foil mesh composite film, according to the aging-resistant aluminum foil mesh composite film according to any one of claims 1 to 5, characterized in that: The following steps are involved: The dynamic cross-linking functional coating is prepared by mixing the polyurethane matrix and the dynamic thiol cross-linking agent in proportion, adding a free radical scavenger, an ultraviolet absorber and a metal coordination cross-linking agent, and stirring evenly; Use a coating machine to apply the dynamic cross-linking functional coating on the surface of the aluminum foil, with a coating thickness of 3-5 μm and a coating temperature of 50-70° C., and cure after coating; The aluminum foil layer and the mesh layer are laminated with a hot melt adhesive at a laminating temperature of 100-120°C and a pressure of 2-4MPa; The composite film is cured at a temperature of 70-80° C. for 6 to 8 hours.

7. The production process of an aging-resistant aluminum foil grid composite film according to claim 6, characterized in that: The dynamically cross-linked functional coating uses nitrogen to protect the environment during the stirring process, and the stirring time is 1 to 2 hours, followed by a degassing treatment for 15 to 30 minutes at a pressure of ≤100Pa.

8. The production process of an aging-resistant aluminum foil grid composite film according to claim 6, characterized in that: The coating curing time is 30 to 60 minutes, and the surface roughness of the coating after curing is controlled to be 0.1 to 0.2 μm.

9. The production process of an aging-resistant aluminum foil grid composite film according to claim 6, characterized in that: In the compounding process, hot melt adhesive modified by nano silicon dioxide particles and silane coupling agent is used, and the compounding speed is 10-20 m / min.

10. The production process of an aging-resistant aluminum foil grid composite film according to claim 6, characterized in that: The post-treatment cooling step of the composite film is slow cooling at room temperature, with a cooling rate of 10-20° C. / h.

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