Bio-based polyamide film for aluminum-plastic film packaging and preparation method of bio-based polyamide film

Abstract

The invention relates to the technical field of packaging materials, in particular to a bio-based polyamide film for aluminum-plastic film packaging and a preparation method of the bio-based polyamide film. The film comprises a coating layer and a bio-based polyamide base material layer, the coating layer is formed by coating the surface of the bio-based polyamide base material layer with acrylic acid coating liquid, and the acrylic acid coating liquid comprises organic silicon modified acrylic resin, polyurethane microspheres, an aziridine cross-linking agent and water; the bio-based polyamide base material layer is composed of three layers of biaxially oriented bio-based polyamide films, and bio-based PA56 and bio-based PA5X in each layer are formed according to a certain proportion. The bio-based PA56 and the bio-based PA5X are cooperatively used and are matched with the acrylic acid coating liquid, so that the stretching ratio of the thin film is reduced, the strength, the toughness and the wear resistance of the thin film are ensured, the electrolyte resistance is improved, and the high pit flushing property of a flat film method is realized.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, and in particular to a bio-based polyamide film for aluminum-plastic film packaging and a preparation method thereof. Background Art

[0002] Aluminum-plastic film is a multi-layer composite soft packaging material composed of aluminum foil, organic film and adhesive. It has the advantages of lightness, high formability, high safety and high barrier properties. It is the preferred material for soft-pack lithium-ion batteries. Its common structure is PET / PA / AL / CPP. Aluminum-plastic film is the key link with the highest barrier in the lithium battery industry chain, and its core technology is in the hands of a few Japanese companies.

[0003] The outer composite PET layer of the aluminum-plastic composite film is mainly used to prevent the electrolyte from dripping onto the surface of the aluminum-plastic film during the lithium battery packaging process, causing the PA layer of the aluminum-plastic film to be corroded by the hydrofluoric acid in the electrolyte.

[0004] The PA layer used in the aluminum-plastic film plays a major mechanical supporting role in the entire aluminum-plastic composite film, and determines the punching depth of the lithium battery outer packaging during the one-step cold punching process. The PA layer requires excellent strength and toughness to protect the aluminum foil in the aluminum-plastic film from being damaged during the cold punching process. It is generally a biaxially oriented polyamide 6 film. At present, the biaxially oriented polyamide 6 film used for domestic aluminum-plastic film adopts the flat film method, and Japanese companies use the tubular film method. Under the same strength, the flat film method uses a single cold drawing, and the molecular orientation is large, resulting in insufficient flexibility, resulting in a punching depth that is worse than the tubular film method, and is limited in application in high-end batteries such as electric vehicles. The advantage of the flat film method lies in the production speed, and the thickness uniformity of the film is better than the tubular film method.

[0005] The black aluminum-plastic composite film requires a layer of black matte oil to be coated on the surface of the aluminum layer where the adhesive layer is connected. However, in the actual production process, the black matte oil coating process will cause about 30-40% loss of the aluminum-plastic film, and the shading degree is difficult to guarantee, which brings certain risks to the quality stability of the aluminum-plastic composite film.

[0006] Bio-based PA is a polymer material synthesized by using renewable biomass (such as glucose, cellulose, and vegetable oil) as raw materials, manufacturing precursors for synthesizing polyamides (such as bio-based lactams, bio-based dibasic acids, and bio-based diamines, etc.) through biological, chemical, and physical means, and then synthesized through polymerization reactions. It has the characteristics of being green, environmentally friendly, and renewable raw materials. For example, compared with traditional PA6 and PA66, bio-based PA56 uses recyclable plant raw materials to reduce the impact of greenhouse gases; compared with traditional petroleum-based PA66, bio-based PA56 can save 50% of non-renewable resources; the glass transition temperature of PA56 is 45-50°C, which is conducive to biaxial stretching; PA56 contains unsaturated hydrogen bonds, retains biological activity, and has a unique Young's modulus value, providing the material with strong and wear-resistant properties and a naturally soft touch. However, PA56 has poor acid and alkali resistance and needs to be improved in aluminum-plastic film applications.

[0007] In summary, how to develop a polyamide film with low light transmittance, excellent pitting performance and electrolyte resistance is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0008] In order to overcome the shortcomings of the prior art, the present invention provides a bio-based polyamide film for aluminum-plastic film packaging and a preparation method thereof. The film has low light transmittance, excellent pitting performance, electrolyte resistance and is green and environmentally friendly.

[0009] The present invention provides a bio-based polyamide film for aluminum-plastic film packaging, comprising a coating layer and a bio-based polyamide substrate layer; The bio-based polyamide substrate layer is a three-layer biaxially stretched bio-based polyamide film, which includes a first substrate layer, a second substrate layer and a third substrate layer from top to bottom, and the first substrate layer is composited with the coating layer; The coating layer is formed by coating an acrylic coating liquid on the surface of the bio-based polyamide substrate layer, and the acrylic coating liquid is prepared by silicone-modified acrylic resin, polyurethane microspheres and aziridine crosslinking agent in a mass ratio of 8-10:3-5:0.3-0.5; The mass ratio of bio-based PA56 to bio-based PA5X in the first substrate layer is 75-90:10-25; The mass ratio of bio-based PA56 to bio-based PA5X in the second substrate layer is 72-89:10-25; The mass ratio of bio-based PA56 to bio-based PA5X in the third substrate layer is 75-90:10-25.

[0010] In a preferred embodiment of the present invention, the first substrate layer components include, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, anti-blocking agent 0.1%-1%, and slip agent 0.1%-1%.

[0011] In a preferred embodiment of the present invention, the second substrate layer comprises, by mass percentage, 72%-89% of bio-based PA56, 10%-25% of bio-based PA5X, and 1%-3% of black pigment.

[0012] In a preferred embodiment of the present invention, the third substrate layer components include, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, anti-blocking agent 0.1%-1%, and lubricating agent 0.1%-1%.

[0013] In a preferred embodiment of the present invention, the bio-based PA5X is one or a combination of bio-based PA510, bio-based PA511, bio-based PA512, bio-based PA513, and bio-based PA514; the melting point of the bio-based PA5X is 180-200°C.

[0014] In a preferred embodiment of the present invention, the black pigment is one or a combination of carbon black, graphene, and organic melanin.

[0015] In a preferred embodiment of the present invention, the opening agent is one or a combination of silicon dioxide, talcum powder, and acrylic microspheres.

[0016] In a preferred embodiment of the present invention, the lubricant is one or a combination of erucamide, oleamide, and ethylene bisstearamide.

[0017] In a preferred embodiment of the present invention, the total thickness of the bio-based polyamide substrate layer is 10-30 μm, and the thickness of the coating layer is 0.5-2 μm.

[0018] The present invention also provides a method for preparing the bio-based polyamide film for aluminum-plastic film packaging as described above, comprising the following steps: S1. Preparation of acrylic acid coating solution: Dissolve 8wt%-10wt% of silicone-modified acrylic resin in water, heat and stir at 60-80°C until the silicone-modified acrylic resin is completely dissolved, and then cool to room temperature to obtain an acrylic acid solution with a concentration of 8wt%-10wt%; Adding 0.3wt%-0.5wt% of an aziridine crosslinking agent and 3wt%-5wt% of polyurethane microspheres to an acrylic acid solution, stirring and ultrasonicating until the mixture is uniformly dispersed, thereby preparing an acrylic acid coating solution; S2, blending the components of the first substrate layer, the second substrate layer and the third substrate layer according to their respective proportions, melt blending, extruding, granulating and drying through a twin-screw extruder to obtain a first masterbatch, a second masterbatch and a third masterbatch respectively, for standby use; wherein the extrusion temperature of the first masterbatch, the second masterbatch and the third masterbatch is 200-280° C.; S3, the first masterbatch obtained in S2 is put into the first extruder to make the first substrate layer; the second masterbatch is put into the second extruder to make the second substrate layer; the third masterbatch is put into the third extruder to make the third substrate layer; wherein the extruder temperature of the first substrate layer, the second substrate layer and the third substrate layer and the temperature of the T-die are 220-280°C; S4, extruding the first substrate layer, the second substrate layer and the third substrate layer in S3, quenching the cast sheet, and MD stretching; wherein the quenching roller temperature is 25-30°C, the MD preheating temperature is 65-85°C, the MD stretching temperature is 60-75°C, and the stretching ratio is 1.8-2.2 times; S5. The surface of the first substrate layer is coated with the acrylic coating liquid prepared in S1, and then TD stretching and heat setting are performed to obtain a coated polyamide film for aluminum-plastic film packaging; wherein the TD preheating temperature is 85-105°C, the TD stretching temperature is 80-100°C, the setting temperature is 180-230°C, and the stretching ratio is 2.5-3.2 times.

[0019] The bio-based polyamide film for aluminum-plastic film packaging and the preparation method thereof provided by the present invention have the following effects compared with the existing technology: The present invention utilizes the high strength, high modulus, wear resistance and softness of bio-based PA56, and synergistically adds long carbon chain bio-based PA5X, which can reduce the water absorption of bio-based PA56 and ensure the dimensional stability of the film on the one hand, and toughen the bio-based PA56 on the other hand to improve its impact performance; while the bio-based PA56 provides excellent coloring performance for the bio-based PA5X, so that a higher content of black pigment can be added, while reducing the light transmittance, there is no need to use black matte oil, reducing manufacturing costs and processes; the two are used in a coordinated manner and acrylic coating liquid is coated on the surface, which not only reduces the stretching ratio of the film and ensures the strength of the film, but also ensures the toughness of the film, reduces the friction coefficient, improves the electrolyte resistance, and achieves high pitting performance of the flat film method; therefore, the production process of the bio-based polyamide film for aluminum-plastic film encapsulation of the present invention is simple, the material is green and environmentally friendly, the light transmittance is low, and the comprehensive performance is excellent, which can reduce the production process of the downstream aluminum-plastic composite film and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a layer structure diagram of the film of Example 1 provided by the present invention.

[0022] Reference numerals: DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0025] The present invention provides the following embodiments and comparative examples: Example 1 The bio-based polyamide film for aluminum-plastic film packaging in this embodiment 1 includes a coating layer 10 and a bio-based polyamide substrate layer 20; the bio-based polyamide substrate layer is a three-layer biaxially oriented bio-based polyamide film, which includes a first substrate layer 21, a second substrate layer 22 and a third substrate layer 23 from top to bottom, and the first substrate layer 21 is composited with the coating layer 10; The coating layer 10 has a thickness of 1 μm; the bio-based polyamide substrate layer 20 has a thickness of 25 μm; Wherein, the first substrate layer 21 components include, by mass percentage: bio-based PA56 89%, bio-based PA512 10%, silicon dioxide 0.5%, ethylene bis stearamide 0.5%; The components of the second substrate layer 22 include, by mass percentage: 88% bio-based PA56, 10% bio-based PA512, and 2% carbon black; The third substrate layer 23 comprises, by mass percentage, 89% bio-based PA56, 10% bio-based PA512, 0.5% silicon dioxide, and 0.5% ethylene bisstearamide; The acrylic coating liquid is made of silicone-modified acrylic resin, 0.4 wt % aziridine crosslinking agent, 4 wt % polyurethane microspheres and water, and has a solid content of 9 wt %.

[0026] Example 2 The structure and thickness of each layer of the bio-based polyamide film for aluminum-plastic film packaging in Example 2 are the same as those in Example 1, and the difference from Example 1 is that: The first substrate layer 21 comprises, by mass percentage: 83% bio-based PA56, 15% bio-based PA512, 1% silicon dioxide, and 1% ethylene bisstearamide; The components of the second substrate layer 22 include, by mass percentage: 88% bio-based PA56, 10% bio-based PA512, and 2% carbon black; The third substrate layer 23 comprises, by mass percentage, 83% bio-based PA56, 15% bio-based PA512, 1% silicon dioxide, and 1% ethylene bisstearamide; The acrylic coating liquid is made of 10 wt % of silicone-modified acrylic resin, 0.5 wt % of aziridine crosslinking agent, 5 wt % of polyurethane microspheres and water, and has a solid content of 10 wt %.

[0027] Example 3 The structure and thickness of each layer of the bio-based polyamide film for aluminum-plastic film packaging in this embodiment 3 are the same as those in embodiment 1, and the difference from embodiment 1 is that: The first substrate layer 21 comprises, by mass percentage, 84.8% bio-based PA56, 15% bio-based PA512, 0.1% silicon dioxide, and 0.1% ethylene bis stearamide; The second substrate layer 22 comprises 84% ​​bio-based PA56, 15% bio-based PA512 and 1% carbon black; The third substrate layer 23 comprises, by mass percentage, 84.8% bio-based PA56, 15% bio-based PA512, 0.1% silicon dioxide, and 0.1% ethylene bis stearamide; The acrylic coating liquid is made of 8wt% silicone-modified acrylic resin, 0.3wt% aziridine crosslinking agent, 3wt% polyurethane microspheres and water, and has a solid content of 8wt%; Example 4 The structure and thickness of each layer of the bio-based polyamide film for aluminum-plastic film packaging in this embodiment 4 are the same as those in embodiment 1, and the difference from embodiment 1 is that: The first substrate layer 21 comprises, by mass percentage: 89% bio-based PA56, 10% bio-based PA510, 0.5% talc, and 0.5% erucamide; The second substrate layer 22 comprises 88% bio-based PA56, 10% bio-based PA510, and 2% organic melanin; The third substrate layer 23 comprises, by mass percentage, 89% bio-based PA56, 10% bio-based PA510, 0.5% talc, and 0.5% erucamide; The acrylic coating liquid is made of 9wt% of silicone-modified acrylic resin, 0.4wt% of aziridine crosslinking agent, 4wt% of polyurethane microspheres and water, and has a solid content of 9wt%.

[0028] The present invention also provides a preparation method of the above-mentioned embodiments 1-4, comprising the following steps: S1. Preparation of acrylic acid coating solution: Dissolve 8wt%-10wt% of silicone-modified acrylic resin in water, heat and stir at 60-80°C until the silicone-modified acrylic resin is completely dissolved, and then cool to room temperature to obtain an acrylic acid solution with a concentration of 8wt%-10wt%; Adding 0.3wt%-0.5wt% of an aziridine crosslinking agent and 3wt%-5wt% of polyurethane microspheres to an acrylic acid solution, stirring and ultrasonicating until the mixture is uniformly dispersed, thereby preparing an acrylic acid coating solution; S2, blending the components of the first substrate layer 21, the second substrate layer 22 and the third substrate layer 23 according to their respective proportions, melt blending, extruding, granulating and drying by a twin-screw extruder to obtain a first masterbatch, a second masterbatch and a third masterbatch respectively, for standby use; wherein the extrusion temperature of the first masterbatch, the second masterbatch and the third masterbatch is 200-280° C.; S3, the first masterbatch obtained in S2 is put into the first extruder to make the first substrate layer 21; the second masterbatch is put into the second extruder to make the second substrate layer 22; the third masterbatch is put into the third extruder to make the third substrate layer 23; wherein the extruder temperature of the first substrate layer 21, the second substrate layer 22 and the third substrate layer 23 and the temperature of the T-die are 220-280°C; S4, extruding the first substrate layer 21, the second substrate layer 22 and the third substrate layer 23 in S3, quenching the cast sheet, and MD stretching; wherein the quenching roller temperature is 25-30°C, the MD preheating temperature is 65-85°C, the MD stretching temperature is 60-75°C, and the stretching ratio is 1.8-2.2 times; S5. The acrylic coating liquid prepared in S1 is coated on the surface of the first substrate layer 21, and then TD stretching and heat setting are performed to obtain a coated polyamide film for aluminum-plastic film; wherein the TD preheating temperature is 85-105°C, the TD stretching temperature is 80-100°C, the setting temperature is 180-230°C, and the stretching ratio is 2.5-3.2 times.

[0029] Comparative Example 1 Comparative Example 1 uses a commonly used biaxially oriented nylon film on the market with a thickness of 25 μm. The specific components and proportions are as follows: The first substrate layer 21 comprises, by mass percentage, 99% PA6, 0.5% silicon dioxide, and 0.5% erucamide; The components of the second substrate layer 22 include, by mass percentage: PA6 100%; The third substrate layer 23 comprises the following components by mass percentage: PA6 99%, silicon dioxide 0.5%, and erucamide 0.5%.

[0030] Comparative Example 2 A coated polyamide film of Comparative Example 2, comprising a coating layer and a polyamide substrate layer from the inside to the outside; The acrylic coating liquid is made of silicone-modified acrylic resin and water, and its solid content is 9wt%; The polyamide substrate layer is a biaxially oriented nylon film commonly used in the market, and its components and proportions are the same as those of Comparative Example 1, and the thickness is 25 μm; The preparation method and coating method of the acrylic coating liquid are the same as those in the embodiment.

[0031] Comparative Example 3 A coated polyamide film of Comparative Example 3, comprising a coating layer and a polyamide substrate layer from the inside to the outside; The acrylic coating liquid is made of silicone-modified acrylic resin, 0.4wt% aziridine crosslinker, 4wt% polyurethane microspheres and water, and its solid content is 9wt%; The polyamide substrate layer is a biaxially oriented nylon film commonly used in the market, and its components and proportions are the same as those of Comparative Example 1, and the thickness is 25 μm; The preparation method and coating method of the acrylic coating liquid are the same as those in the embodiment.

[0032] Comparative Example 4 The structure, thickness of each layer, composition and preparation method of acrylic coating liquid, preparation method and coating method of polyamide substrate layer of the coated polyamide film for aluminum-plastic film packaging of Comparative Example 4 are the same as those of Example 1, and the difference from Example 1 is that: The bio-based PA56 component in the first substrate layer, the second substrate layer and the third substrate layer of Example 1 was replaced with PA6, and the extrusion temperature of each layer and the masterbatch was controlled between 180-240°C.

[0033] Comparative Example 5 The structure, thickness of each layer, composition and preparation method of acrylic coating liquid, preparation method and coating method of polyamide substrate layer of the coated polyamide film for aluminum-plastic film packaging of Comparative Example 5 are the same as those of Example 1, and the difference from Example 1 is that: The first substrate layer comprises, by mass percentage, 99% bio-based PA56, 0.5% silicon dioxide, and 0.5% ethylene bisstearamide; The second substrate layer components include, by mass percentage: bio-based PA56 98%, carbon black 2%; The third substrate layer components include, by mass percentage: 99% bio-based PA56, 0.5% silicon dioxide, and 0.5% ethylene bisstearamide.

[0034] Comparative Example 6 The structure, thickness of each layer, composition and preparation method of acrylic coating liquid, preparation method and coating method of polyamide substrate layer of the coated polyamide film for aluminum-plastic film packaging of Comparative Example 6 are the same as those of Example 1, and the difference from Example 1 is that: The first substrate layer components include, by mass percentage: 94% bio-based PA56, 5% bio-based PA512, 0.5% silicon dioxide, and 0.5% ethylene bis stearamide; The second substrate layer comprises 93% bio-based PA56, 5% bio-based PA512 and 2% carbon black; The third substrate layer components include, by mass percentage, 94% bio-based PA56, 5% bio-based PA512, 0.5% silicon dioxide, and 0.5% ethylene bisstearamide.

[0035] The films prepared in the embodiments and comparative examples were subjected to performance tests, and the specific test methods were as follows: Thickness: Tested in accordance with GB / T20220-2006 "Average thickness of plastic film and sheet samples, average thickness of rolls and unit mass area"; Haze and light transmittance: Tested in accordance with GB / T2410-2008 "Standard for Determination of Light Transmittance and Haze of Transparent Plastics"; Friction coefficient: Tested in accordance with GB / T10006-1988 "Determination of friction coefficient of plastic films and sheets"; Tensile strength and elongation at break: tested in accordance with GB / T 1040-3 "Determination of tensile properties of plastics Part 3: Test conditions for thin plastics and sheets"; Punching depth test: The polyamide films of the embodiment and the comparative example were used to prepare PA / AL / CPP composite films. The punching mold used in the lithium-ion battery aluminum-plastic packaging film factory was used to clamp the PA / AL / CPP composite film. The film was tested using punching heads of different depths until the film was broken. Electrolyte resistance test: Use commercially available lithium battery electrolyte, drop the same amount of electrolyte onto the surface of the biaxially oriented polyamide film prepared in the above example and the film in the comparative example, and place them at 25°C RH50% for 2 hours, then wipe off the electrolyte with paper and observe the surface corrosion. Resistance to electrolyte corrosion is indicated by "○", and resistance to electrolyte corrosion is indicated by "△".

[0036] The test results are shown in Table 1: Table 1

[0037] As shown in Table 1, compared with Comparative Example 1 which only uses the commonly used biaxially oriented nylon film on the market, the films provided by Examples 1-4 have a small friction coefficient, low gloss and light transmittance, good light-shielding performance, good tensile strength and ductility, and after being compounded with aluminum foil and PE, the pit depth and electrolyte resistance are improved; The acrylic coating liquid of the coating layer of Comparative Example 2 does not contain polyurethane microspheres and aziridine crosslinking agent, and the substrate layer uses a biaxially oriented nylon film commonly used in the market. Compared with Comparative Example 2, the films provided by Examples 1-4 have low gloss and light transmittance, good light-shielding performance, good tensile strength and ductility, and after being compounded with aluminum foil and PE, the punching depth and electrolyte resistance are improved; The coating layer of Comparative Example 3 uses the acrylic coating liquid prepared by the present invention, and the substrate layer uses a biaxially oriented nylon film commonly used in the market. Compared with Comparative Example 3, the tensile strength and ductility of the films provided by Examples 1-4 are significantly improved, the light transmittance is reduced, and after being compounded with aluminum foil and PE, the pit depth is increased; The coating layer of Comparative Example 4 uses the acrylic coating liquid prepared by the present invention, and the substrate layer uses the PA6 component. Compared with Comparative Example 4, the tensile strength of the film provided by Examples 1-4 is improved, and after being compounded with aluminum foil and PE, the depth of the punching pit is improved; The coating layer of Comparative Example 5 uses the acrylic coating liquid prepared by the present invention, and the bio-based PA512 is not added to the composition ratio of the substrate layer. Compared with Comparative Example 5, after the films provided by Examples 1-4 are compounded with aluminum foil and PE, the depth of the punching pits is increased; The coating layer of Comparative Example 6 uses the acrylic coating liquid prepared by the present invention, and the composition ratio of the substrate layer is changed. Compared with Comparative Example 6, after the film provided by Examples 1-4 is compounded with aluminum foil and PE, the depth of the crater is increased; In summary, the bio-based polyamide film for aluminum-plastic film packaging of the present invention has high tensile strength and ductility, indicating good reliability and durability, small friction coefficient, low gloss, and good light-shielding performance. At the same time, after the film is compounded with aluminum foil and PE, it has good pitting performance and good electrolyte resistance. The material is green and environmentally friendly and is particularly suitable for aluminum-plastic composite film flexible packaging.

[0038] Although the terms such as bio-based polyamide film, substrate layer, coating layer and acrylic coating liquid are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bio-based polyamide film for aluminum-plastic film packaging, characterized in that: including a coating layer and a bio-based polyamide substrate layer; The bio-based polyamide substrate layer is a three-layer biaxially stretched bio-based polyamide film, which includes a first substrate layer, a second substrate layer and a third substrate layer from top to bottom, and the first substrate layer is composited with the coating layer; The coating layer is formed by coating an acrylic coating liquid on the surface of the bio-based polyamide substrate layer, and the acrylic coating liquid is prepared by silicone-modified acrylic resin, polyurethane microspheres and aziridine crosslinking agent in a mass ratio of 8-10:3-5:0.3-0.5; The mass ratio of bio-based PA56 to bio-based PA5X in the first substrate layer is 75-90:10-25; The mass ratio of bio-based PA56 to bio-based PA5X in the second substrate layer is 72-89:10-25; The mass ratio of bio-based PA56 to bio-based PA5X in the third substrate layer is 75-90:10-25.

2. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The first substrate layer components include, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, anti-blocking agent 0.1%-1%, and lubricating agent 0.1%-1%.

3. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The second substrate layer components include, by mass percentage: bio-based PA56 72%-89%, bio-based PA5X 10%-25%, and black pigment 1%-3%.

4. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The third substrate layer components include, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, anti-blocking agent 0.1%-1%, and lubricating agent 0.1%-1%.

5. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The bio-based PA5X is one or a combination of bio-based PA510, bio-based PA511, bio-based PA512, bio-based PA513, and bio-based PA514; the melting point of the bio-based PA5X is 180-200°C.

6. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The black pigment is one or a combination of carbon black, graphene, and organic melanin.

7. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The opening agent is one or a combination of silicon dioxide, talcum powder, and acrylic microspheres.

8. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The lubricant is one or a combination of erucamide, oleamide, and ethylene bisstearamide.

9. The bio-based polyamide film for aluminum-plastic film packaging according to claim 1, characterized in that: The total thickness of the bio-based polyamide substrate layer is 10-30 μm, and the thickness of the coating layer is 0.5-2 μm.

10. A method for preparing a bio-based polyamide film for aluminum-plastic film packaging according to any one of claims 1 to 9, characterized in that : Includes the following steps: S1. Preparation of acrylic acid coating solution: Dissolve 8wt%-10wt% of silicone-modified acrylic resin in water, heat and stir at 60-80°C until the silicone-modified acrylic resin is completely dissolved, and then cool to room temperature to obtain an acrylic acid solution with a concentration of 8wt%-10wt%; Adding 0.3wt%-0.5wt% of an aziridine crosslinking agent and 3wt%-5wt% of polyurethane microspheres to an acrylic acid solution, stirring and ultrasonicating until the mixture is uniformly dispersed, thereby preparing an acrylic acid coating solution; S2, blending the components of the first substrate layer, the second substrate layer and the third substrate layer according to their respective proportions, melt blending, extruding, granulating and drying through a twin-screw extruder to obtain a first masterbatch, a second masterbatch and a third masterbatch respectively, for standby use; wherein the extrusion temperature of the first masterbatch, the second masterbatch and the third masterbatch is 200-280° C.; S3, the first masterbatch obtained in S2 is put into the first extruder to make the first substrate layer; the second masterbatch is put into the second extruder to make the second substrate layer; the third masterbatch is put into the third extruder to make the third substrate layer; wherein the extruder temperature of the first substrate layer, the second substrate layer and the third substrate layer and the temperature of the T-die are 220-280°C; S4, extruding the first substrate layer, the second substrate layer and the third substrate layer in S3, quenching the cast sheet, and MD stretching; wherein the quenching roller temperature is 25-30°C, the MD preheating temperature is 65-85°C, the MD stretching temperature is 60-75°C, and the stretching ratio is 1.8-2.2 times; S5. The surface of the first substrate layer is coated with the acrylic coating liquid prepared in S1, and then TD stretching and heat setting are performed to obtain a coated polyamide film for aluminum-plastic film packaging; wherein the TD preheating temperature is 85-105°C, the TD stretching temperature is 80-100°C, the setting temperature is 180-230°C, and the stretching ratio is 2.5-3.2 times.

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