Protective film, preparation method thereof and refrigerator

Abstract

The invention discloses a protective film, a preparation method thereof and a refrigerator, and belongs to the field of protective films. The invention provides a protective film, which is used for protecting the surface of a metal part and comprises a substrate, a filler and an adhesive, the filler comprises diatomite and chitosan, and the adhesive comprises a metal organic framework. The protective film is applied to the aspect of household appliance protection, solves the problems that a special-shaped metal part protective film is difficult to paste and easy to generate bubbles, and has the characteristics of excellent air permeability, adhesiveness and convenience in operation.

Description

Technical Field

[0001] This invention belongs to the field of protective films, and particularly relates to a protective film, its preparation method, and a refrigerator. Background Technology

[0002] During the production and assembly of home appliances, parts often suffer scratches and abrasions, which can negatively impact consumer purchasing decisions. To prevent this, a protective film is typically applied to the surface of metal and plastic injection-molded parts.

[0003] Chinese patent CN119350992A discloses a stainless steel PE protective film and its preparation method. The protective film adopts a multilayer structure optimized by mixing LLDPE and LDPE, and adds components such as titanium dioxide, nano clay, nucleating agent, antioxidant and lubricant to significantly improve the overall performance of the film and achieve protection for stainless steel.

[0004] However, due to their varied shapes, metal parts cannot be machine-coated, and in many cases, manual coating is the only option. However, manual application of protective film often results in uneven film surfaces and numerous air bubbles, a common problem in the industry with no universal solution currently available. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the technical problem to be solved by the present invention is that the protective film for irregularly shaped metal parts is difficult to apply and is prone to air bubbles. The present invention proposes a protective film with excellent air permeability, adhesion and easy operation, its preparation method and refrigerator.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows: This invention provides a protective film for surface protection of metal parts. The protective film includes a substrate, fillers, and adhesives. The fillers include diatomaceous earth and chitosan, and the adhesives include metal-organic frameworks.

[0007] The present invention also provides a method for preparing the above-mentioned protective film, comprising: coating an adhesive solution containing a metal-organic framework onto a thin film, drying and growing a covalent organic framework using microwave-assisted heating; the thin film includes a filler.

[0008] In some embodiments, the heating conditions for microwave-assisted heating are: microwave irradiation power of 95-105W, reaction temperature of 95-105℃, and time of 4-5 minutes.

[0009] In some embodiments, the adhesive solution is prepared by the following method: Nano-silica particles and metal oxides are added to an aqueous solution of polyacrylic acid and stirred thoroughly. Then, propanol is added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The zeolite imidazole ester framework material was dissolved in methanol at 60-100℃. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles. The mixture was stirred thoroughly and mixed evenly to obtain a mixed solution.

[0010] In some embodiments, a tackifying resin is added to the mixed solution and stirred thoroughly to obtain an adhesive solution.

[0011] In some embodiments, the thin film is prepared by the following method: Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is uniformly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is then granulated to obtain composite granules. Film extrusion: Composite granules, antioxidants, and LDPE are fed into a blown film extruder, blown in a die through a twin-screw extruder, and then cooled, pressed by traction wheels, and edge-planed to obtain a film.

[0012] In some embodiments, the granulation of the permeable filler includes: setting the heating temperature to 165-180°C, the die temperature to 160-165°C, and the rotation speed to 50 rpm in a twin-screw granulator, demolding, cooling, and then entering a pelletizer to obtain composite granules; In film extrusion, the screw temperature is 160-185℃ and the rotation speed is 45rpm. The film is blown in a die at 165-175℃, cooled, pressed by traction wheels, and edge-planing to obtain the film.

[0013] In some embodiments, the metal oxide is selected from at least one of zinc oxide, aluminum oxide, and magnesium oxide; the zeolite imidazole ester skeleton material is selected from one of 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, and benzimidazole; and the tackifying resin is selected from at least one of rosin resins and terpene resins. The molar ratio of nano-silica particles to metal oxides is 1:0.5-1.

[0014] In some embodiments, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 2246, antioxidant 168, antioxidant 622, antioxidant 944, antioxidant 3114, antioxidant 626, and antioxidant 618.

[0015] The present invention also provides a refrigerator, wherein the surface of the metal parts of the refrigerator is provided with a protective film of any of the above-mentioned technical solutions.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a protective film in which the framework material of a metal-organic framework is embedded in the filler, exerting a "molecular highway" effect to significantly increase the gas throughput, thereby improving the gas permeation rate of the protective film and effectively preventing the formation of bubbles. At the same time, for irregularly shaped metal parts, the contact area between the protective film and the metal part is limited, and usually a large amount of adhesive is required to achieve effective bonding. In this invention, the metal-organic framework loaded on the adhesive can coordinate with the oxide layer or free metal ions on the surface of the metal part to form a strong hydrogen bond network, achieving efficient bonding between the protective film and the part in a limited area. Detailed Implementation

[0017] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0018] This invention provides a protective film for surface protection of metal parts.

[0019] During the production and assembly of home appliances, a protective film is often applied to the surface of metal and plastic injection-molded parts to prevent scratches from bumps and abrasions that could affect consumer purchasing decisions. Due to their varied shapes, metal parts cannot be machine-coated, and in many cases, manual coating is the only option. However, manual application of protective film often results in uneven surfaces and numerous air bubbles.

[0020] A protective film includes a substrate. In some embodiments, the protective film for a refrigerator uses a polyethylene material as the substrate.

[0021] A protective membrane, comprising filler.

[0022] In some embodiments, the filler includes diatomaceous earth. Ultrafine diatomaceous earth naturally possesses a honeycomb-like porous structure with high specific surface area and porosity, enabling effective adsorption of some gases. Furthermore, the interconnected pores form a three-dimensional network, allowing gases to permeate freely and preventing internal agglomeration or blockage. Simultaneously, diatomaceous earth is a natural mineral, non-toxic and harmless, meeting environmental material standards.

[0023] In some embodiments, the filler includes chitosan. The microporous structure formed between chitosan molecular chains allows gas to pass through freely while blocking liquid water permeation. Chitosan is abundant and its extraction process is mature; industrial-grade chitosan is inexpensive. During film formation, the chitosan molecular chains intertwine to form a three-dimensional network structure. This structure provides mechanical support while maintaining appropriate intermolecular interactions, avoiding brittleness caused by excessive cross-linking, and significantly improving the mechanical properties of the film. Using ultrafine diatomaceous earth and chitosan as fillers can improve the gas permeability and mechanical properties of the film.

[0024] A protective film, comprising an adhesive.

[0025] In practical applications, protective films are often applied manually to irregularly shaped metal parts. This manual application frequently results in numerous air bubbles within the film, affecting the product's appearance. Conventional venting methods include puncturing and manually squeezing out air bubbles. However, puncturing can easily scratch the parts, reducing the film's protective capabilities; manually squeezing out air bubbles requires relatively low adhesion between the protective film and the part, but low viscosity can negatively impact the film's protective effect and significantly reduce production efficiency.

[0026] In addition, for irregularly shaped metal parts, the effective contact area between the protective film and the metal part usually requires a large amount of adhesive to achieve effective bonding, which further exacerbates the formation of bubbles.

[0027] In some embodiments, the adhesive comprises a metal-organic framework.

[0028] Metal-organic frameworks (MOFs) are three-dimensional porous structures formed by the self-assembly of metal ions and organic ligands. They have a very high specific surface area, far exceeding that of traditional adsorbent materials (such as activated carbon). This structure provides dense adsorption sites for gas molecules, enabling efficient gas capture. In addition, the metal nodes in the MOF can form coordination bonds with unsaturated atoms on the surface of metal materials, achieving atomic-level interfacial connections and effectively improving the adhesion between the protective film and the metal components.

[0029] In the above technical solution, the metal-organic framework, as a component of the adhesive, can adsorb gases and enhance the adhesion between the film and the metal. After the protective film provided by this invention is applied to the metal component, it can absorb or clear air bubbles through the action of the internal filler and the synergistic effect of the covalent organic framework, thereby effectively adhering the protective film to the metal component. At the same time, since the adhesive in this invention is also loaded with a metal-organic framework, it can coordinate with the oxide layer or free metal ions on the surface of the metal component to form a strong hydrogen bond network, achieving efficient adhesion between the protective film and the component in a limited area.

[0030] Furthermore, the framework material in the metal-organic framework is embedded in the filler containing diatomaceous earth and chitosan, exerting a "molecular highway" effect to significantly increase gas flux, thereby improving the gas permeation rate of the protective membrane and effectively preventing bubble formation. The film prepared by this invention, composed of multiple components, can achieve gas diffusion through the three-dimensional network structure constructed by the internal filler after being attached to a metal component, and can also achieve gas adsorption through the porous structure of diatomaceous earth, metal-organic framework, etc., ultimately eliminating bubbles between the film and the metal component and achieving a smooth film adhesion.

[0031] The present invention also provides a method for preparing the above-mentioned protective film, comprising: coating an adhesive solution containing a metal-organic framework onto a thin film, drying and growing a covalent organic framework using microwave-assisted heating; the thin film includes a filler.

[0032] Traditionally, adhesive drying utilizes air convection to allow solvents to evaporate naturally or accelerates evaporation through hot air or infrared heating. However, these methods suffer from low drying efficiency and high energy consumption. Microwave-assisted drying, by reducing solvent usage, energy consumption, and reaction time, meets energy conservation and emission reduction requirements, achieving the drying and curing of colloids. Furthermore, microwave-assisted drying can significantly shorten the reaction time of metal-organic frameworks, and the rapid heating characteristics of microwaves enable continuous production while also evaporating the solvent.

[0033] In some embodiments, the heating conditions for microwave-assisted heating are: microwave irradiation power of 95-105W.

[0034] It is understandable that the microwave irradiation power can be any value within the range of 96W, 97W, 98W, 99W, 100W, 101W, 102W, 103W, 104W, etc. At these microwave irradiation powers, ordered crystal growth is facilitated, crystal defects are reduced, excessive nucleation is suppressed, slow growth is promoted, and a primary metal-organic framework is generated on the surface of the adhesive. Furthermore, at this irradiation power, a strong connection can be achieved between the metal-organic framework and fillers such as chitosan and diatomaceous earth.

[0035] In some embodiments, the heating conditions for microwave-assisted heating are: a reaction temperature of 95-105°C.

[0036] Understandably, the reaction temperature can also be any value within the range of 96℃, 97℃, 98℃, 99℃, 100℃, 101℃, 102℃, 103℃, 104℃, etc. Crystal growth kinetics are optimal at these temperatures; too low a temperature will slow crystal growth and prolong the formation cycle; too high a temperature will cause crystal growth to be too rapid, leading to defect accumulation or ligand decomposition.

[0037] In some embodiments, the heating conditions for microwave-assisted heating are: a time of 4-5 minutes.

[0038] In some embodiments, replacing the rollers with a textured rollers during the subsequent film winding process can create a regular dotted structure in the adhesive material inside the film, which can further improve the film's air permeability.

[0039] In some embodiments, the adhesive solution is prepared by the following method: Nano-silica particles and metal oxides are added to an aqueous solution of polyacrylic acid and stirred thoroughly. Then, propanol is added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The zeolite imidazole ester framework material was dissolved in methanol at 60-100℃. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles. The mixture was stirred thoroughly and mixed evenly to obtain a mixed solution. Add tackifying resin to the mixed solution and stir thoroughly to obtain an adhesive solution.

[0040] The adhesive solution prepared by the above method achieves efficient bonding between the adhesive solution and the metal parts from multiple dimensions, including metal particles, metal-organic frameworks, and tackifying resins.

[0041] In some embodiments, the thin film is prepared by the following method: Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is uniformly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is then granulated to obtain composite granules. Film extrusion: Composite granules, antioxidants, and LDPE are fed into a blown film extruder, blown in a die through a twin-screw extruder, and then cooled, pressed by traction wheels, and edge-planed to obtain a film.

[0042] During the protective film application process, air bubbles are mainly encased inside the protective film. The metal-organic framework has the functions of gas adsorption and increased adhesion, and its addition to the adhesive can make it work more efficiently.

[0043] In some embodiments, the granulation of the permeable filler includes setting a heating temperature of 165-180°C in a twin-screw granulator. It is understood that the heating temperature can also be any value within the range of 170°C, 175°C, or similar temperatures.

[0044] In some embodiments, the granulation process for the permeable filler includes: in a twin-screw granulator, the die temperature is 160-165°C, the rotation speed is 50 rpm, the material exits the die, cools, and then enters a pelletizer to obtain composite granules. It is understood that the die temperature can also be any value within the range of 161°C, 162°C, 163°C, and 164°C.

[0045] In some embodiments, during film extrusion, the screw temperature is 160-185°C and the rotation speed is 45 rpm. It is understood that the screw temperature can also be any value within the range of 170°C, 175°C, 180°C, or 175°C.

[0046] In some embodiments, during film extrusion, the film is blown in a die at 165-175°C, cooled, pressed by traction rollers, and edge-planed to obtain the film. It is understood that this temperature can also be any value within the range of 167°C, 169°C, 171°C, 173°C, and so on.

[0047] In some embodiments, the metal oxide is selected from at least one of zinc oxide, aluminum oxide, and magnesium oxide.

[0048] In some embodiments, the zeolite imidazole ester skeleton material is selected from one of 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, and benzimidazole.

[0049] In some embodiments, the tackifying resin is selected from at least one of rosin resins and terpene resins.

[0050] In some embodiments, the molar ratio of nano-silica particles to metal oxides is 1:0.5-1. It is understood that the molar ratio of nano-silica particles to metal oxides can also be any value within the range of 1:0.6, 1:0.7, 1:0.8, 1:0.9, etc.

[0051] In some embodiments, the antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 2246, antioxidant 168, antioxidant 622, antioxidant 944, antioxidant 3114, antioxidant 626, and antioxidant 618.

[0052] The present invention also provides a refrigerator, wherein the surface of the metal parts of the refrigerator is provided with a protective film of any of the above-mentioned technical solutions.

[0053] To provide a clearer and more detailed description of the protective film, its preparation method, and the refrigerator provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0054] Example 1 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is zinc oxide, and the molar ratio of nano-silica particles to the metal oxide is 1:1.

[0055] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is 2-methylimidazole, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:1. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is rosin resin.

[0056] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 165℃, the die temperature is set to 160℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:1.

[0057] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 170℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0058] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 15 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0059] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0060] Example 2 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is aluminum oxide, and the molar ratio of nano-silica particles to metal oxide is 1:1.

[0061] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is 2-ethylimidazole, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:1.1. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is rosin resin.

[0062] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, and the heating temperature is set to 170℃, the die temperature is set to 170℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:1.5.

[0063] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 172℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0064] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 12 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0065] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0066] Example 3 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is magnesium oxide, and the molar ratio of nano-silica particles to metal oxide is 1:1.

[0067] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is 2-propylimidazolium, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:0.9. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is a terpene resin.

[0068] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 171℃, the die temperature is set to 162℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:0.95.

[0069] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 175℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0070] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 10 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0071] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0072] Example 4 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is zinc oxide, and the molar ratio of nano-silica particles to metal oxide is 1:0.5.

[0073] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is 2-methylimidazole, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:1.1. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is rosin resin.

[0074] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 169℃, the die temperature is set to 162℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:0.8.

[0075] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 184℃ and the speed is 45rpm, blown in the mold at 174℃, and then cooled, pressed by the traction wheel and edge planed.

[0076] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 8 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0077] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0078] Example 5 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is zinc oxide, and the molar ratio of nano-silica particles to metal oxide is 1:0.75.

[0079] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is 2-methylimidazole, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:1.05. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is rosin resin.

[0080] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 170℃, the die temperature is set to 164℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:1.1.

[0081] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 180℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0082] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 4 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0083] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0084] Example 6 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is zinc oxide, and the molar ratio of nano-silica particles to the metal oxide is 1:1.

[0085] (2) Synthesis of metal-organic framework: First, the zeolite imidazole ester framework material was dissolved in methanol at 70°C. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles and stirred thoroughly to mix evenly. The zeolite imidazole ester skeleton material is benzimidazole, and the molar ratio of the zeolite imidazole ester skeleton material to the polyacrylic acid spherical particles is 1:1.01. (3) Preparation of adhesive solution: Add tackifying resin to the obtained mixed solution, stir thoroughly, and set aside; The tackifying resin is a terpene resin.

[0086] (4) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 171℃, the die temperature is set to 161℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:1.01.

[0087] (5) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 180℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0088] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 2 parts, and the amount of antioxidant is 2 parts; the antioxidant is antioxidant 1010.

[0089] (6) Colloid coating and film forming: The prepared adhesive solution containing metal-organic framework raw material is coated (roller coating or doctor blade coating) on ​​the film. The colloid is dried and the covalent organic framework is grown by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film. Finally, it is wound and packaged.

[0090] Comparative Example 1 (1) Preparation of adhesive solution: Dissolve the tackifying resin, stir thoroughly, and set aside; the tackifying resin is a terpene resin.

[0091] (2) Granulation of breathable filler: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is evenly dispersed in water, and ultrasonic treatment is used to avoid agglomeration. After the two phases are mixed, glutaraldehyde is added and stirred until a homogeneous slurry is formed. The slurry is added to a twin-screw granulator, the heating temperature is set to 175℃, the die temperature is set to 164℃, and the rotation speed is set to 50rpm. After demolding and cooling, the granules are fed into a pelletizer to obtain composite granules for later use. The molar ratio of chitosan to diatomaceous earth is 1:1.

[0092] (3) Film extrusion: The breathable filler, antioxidant and LDPE are fed into the blown film unit, passed through the twin screw extruder, the screw temperature is 180℃ and the speed is 45rpm, blown in the mold at 170℃, and then cooled, pressed by the traction wheel and edge planed.

[0093] By weight, the amount of LDPE is 100 parts, the amount of breathable filler is 15 parts, and the amount of antioxidant is 3 parts; the antioxidant is antioxidant 1010.

[0094] (4) Colloid coating and film forming: The adhesive solution is coated (roller coating or doctor blade coating) on ​​the film, and the colloid is dried by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film, and then it is wound and packaged.

[0095] Comparative Example 2 (1) Synthesis of polyacrylic acid metal oxide nanoparticles: First, nano-silica particles and metal oxides were added to an aqueous solution of polyacrylic acid and stirred thoroughly to obtain a mixed solution. Then, propanol was added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The metal oxide is zinc oxide, and the molar ratio of nano-silica particles to the metal oxide is 1:1.

[0096] (2) Preparation of adhesive solution: Dissolve polyacrylic acid spherical particles with tackifying resin, stir thoroughly, and set aside; The tackifying resin is a terpene resin.

[0097] (3) Film extrusion: LDPE is fed into the blown film unit, passes through a twin-screw extruder, the screw temperature is 180℃, the speed is 45rpm, and it is blown in a mold at 170℃. After cooling, traction wheel pressing and edge planing treatment.

[0098] The amount of LDPE used is 100 parts by weight.

[0099] (6) Colloid coating and film forming: The prepared adhesive solution is coated (roller coating or doctor blade coating) on ​​the film, and the colloid is dried by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film, and then it is wound and packaged.

[0100] Comparative Example 3 (1) Preparation of adhesive solution: Dissolve the tackifying resin, stir thoroughly, and set aside; the tackifying resin is rosin resin.

[0101] (2) Film extrusion: LDPE is fed into the blown film unit, passes through a twin-screw extruder, the screw temperature is 180℃, the speed is 45rpm, and it is blown in a mold at 170℃. After cooling, traction wheel pressing and edge planing treatment.

[0102] The amount of LDPE used is 100 parts by weight.

[0103] (3) Colloid coating and film forming: The adhesive solution is coated (roller coating or doctor blade coating) on ​​the film, and the colloid is dried by microwave-assisted heating. Then the film is passed through a textured wheel with several grooves on the surface to prepare a textured film, and then it is wound and packaged.

[0104] Comparative Example 4 Same as Example 1, except that hot air is used to dry the colloid during colloid coating and film forming.

[0105] The raw materials and compositions of the examples and comparative examples are shown in Tables 1 and 2.

[0106] Table 1. Raw materials and composition of the adhesives used in the examples and comparative examples.

[0107] Table 2. Raw materials and composition for granulation and film extrusion in Examples and Comparative Examples

[0108] Performance testing Example 1 6. The protective films prepared in Examples 1-4 were subjected to performance testing according to GB / T1040.1. In 2006, tensile strength and elongation were tested (test conditions: 300 mm / min). Gas permeability was tested according to GB / T 1038 and according to GB / T 2792. 2014 180° peel force test (test conditions: 430BA plate, 300 mm / min after 10 min at room temperature).

[0109] The examples and comparative test results are shown in Table 3.

[0110] Table 3 Performance Test Results

[0111] The results show that, compared to the protective film without the added breathable filler, the addition of the filler significantly improves the tensile strength, elongation at break, and gas permeability of the protective film. Furthermore, the addition of a metal-organic framework (MOF) to the adhesive significantly enhances the adhesion strength between the protective film and the metal substrate, enabling the protective film to function more sustainably and stably. Meanwhile, comparing Example 1 and Comparative Example 4, it was found that under hot air drying conditions, the gas permeability and peel strength of the protective film significantly decreased, indicating that the growth of the MOF was incomplete under hot air drying conditions, resulting in reduced adhesion to the metal sheet and decreased gas permeability.

Claims

1. A protective film, characterized in that, For surface protection of metal parts, the protective film includes a substrate, filler and adhesive; the filler includes diatomaceous earth and chitosan, and the adhesive includes a metal-organic framework.

2. The method for preparing the protective film according to claim 1, characterized in that, include: An adhesive solution containing the metal-organic framework is coated onto a thin film, and the film is dried and covalently grown using microwave-assisted heating; the thin film includes the filler.

3. The method for preparing the protective film according to claim 2, characterized in that, The heating conditions for microwave-assisted heating are: microwave irradiation power of 95-105W, reaction temperature of 95-105℃, and time of 4-5 minutes.

4. The method for preparing the protective film according to claim 2, characterized in that, The adhesive solution is prepared by the following method: Nano-silica particles and metal oxides are added to an aqueous solution of polyacrylic acid and stirred thoroughly. Then, propanol is added dropwise to form polyacrylic acid spherical particles loaded with nanoparticles through self-assembly. The zeolite imidazole ester framework material was dissolved in methanol at 60-100℃. Then, the resulting zeolite imidazole ester framework material solution was injected into a methanol solution containing polyacrylic acid spherical particles. The mixture was stirred thoroughly and mixed evenly to obtain a mixed solution.

5. The method for preparing the protective film according to claim 4, characterized in that, Add tackifying resin to the mixed solution and stir thoroughly to obtain the adhesive solution.

6. The method for preparing the protective film according to claim 2, characterized in that, The thin film was prepared by the following method: Breathable filler granulation: Chitosan is dissolved in dilute acetic acid solution, diatomaceous earth is uniformly dispersed in water, ultrasonic treatment is used to avoid agglomeration, glutaraldehyde is added after the two phases are mixed, and the mixture is stirred until a homogeneous slurry is formed. The slurry is then granulated to obtain composite granules. Film extrusion: The composite granules, antioxidant, and LDPE are fed into a blown film extruder, blown in a die through a twin-screw extruder, and then cooled, pressed by traction wheels, and edge-planed to obtain the film.

7. The method for preparing the protective film according to claim 6, characterized in that, In the granulation of the permeable filler, the granulation includes: setting the heating temperature to 165-180℃, the die temperature to 160-165℃, and the rotation speed to 50rpm in a twin-screw granulator, extruding the material from the die, cooling it, and then feeding it into a pelletizer to obtain the composite granules; In the film extrusion process, the screw temperature is 160-185℃, the rotation speed is 45 rpm, and the film is blown in a die at 165-175℃. After cooling, traction wheel pressing, and edge planing, the film is obtained.

8. The method for preparing the protective film according to claim 5, characterized in that, The metal oxide is selected from at least one of zinc oxide, aluminum oxide, and magnesium oxide; the zeolite imidazole ester skeleton material is selected from one of 2-methylimidazolium, 2-ethylimidazolium, 2-propylimidazolium, and benzimidazole; the tackifying resin is selected from at least one of rosin resins and terpene resins. The molar ratio of the nano-silica particles to the metal oxide is 1:0.5-1.

9. The method for preparing the protective film according to claim 6, characterized in that, The antioxidant is selected from at least one of antioxidant 1010, antioxidant 1076, antioxidant 2246, antioxidant 168, antioxidant 622, antioxidant 944, antioxidant 3114, antioxidant 626, and antioxidant 618.

10. A refrigerator, characterized in that, The surface of the metal parts of the refrigerator is provided with the protective film as described in claim 1.

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