A bio-based polyamide film for aluminum laminated packaging and a method for preparing the same

Abstract

The present application relates to the technical field of packaging materials, and particularly relates to a bio-based polyamide film for aluminum-plastic film packaging and a preparation method thereof. The film comprises a coating layer and a bio-based polyamide substrate layer; the coating layer is formed by coating an acrylic coating liquid on the surface of the bio-based polyamide substrate layer, the acrylic coating liquid comprises an organic silicon modified acrylic resin, polyurethane microspheres, an aziridine crosslinking agent and water; the bio-based polyamide substrate layer is composed of three layers of biaxially stretched bio-based polyamide film, and bio-based PA56 and bio-based PA5X in each layer are composed in a certain ratio. The bio-based PA56 and the bio-based PA5X are used in cooperation with the acrylic coating liquid, so that the stretching ratio of the film is reduced, the strength, toughness and wear resistance of the film are ensured, the electrolyte resistance is improved, and the high pit property of the flat film method is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of packaging materials, and particularly relates to a bio-based polyamide film for aluminum-plastic film packaging and a preparation method thereof. BACKGROUND

[0002] The aluminum-plastic film is a multi-layer composite soft packaging material composed of an aluminum foil, an organic film and an adhesive, has the advantages of lightness, high formability, high safety and high barrier property, and is the first choice for soft packaging of lithium ion batteries. The common structure thereof is PET / PA / AL / CPP. The aluminum-plastic film is the key link with the highest barrier in the lithium battery industry chain, and the core technology thereof is mastered by a few Japanese enterprises.

[0003] The PET layer in the outer layer of the aluminum-plastic composite film is mainly used to prevent the electrolyte from dropping on the surface of the aluminum-plastic film during the packaging process of the lithium battery, so as to prevent the PA layer of the aluminum-plastic film from being corroded by the hydrofluoric acid in the electrolyte.

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

[0005] The black aluminum-plastic composite film needs to be coated with a layer of black matte oil on the surface of the aluminum layer at the bonding layer, but in the actual production process, the coating process of the black matte oil will cause about 30-40% of the aluminum-plastic film to be lost, 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 kind of polymer material synthesized by using renewable biomass (such as glucose, cellulose, vegetable oil) as raw material, through biological, chemical and physical means to manufacture precursors (such as bio-based lactam, bio-based diacid, bio-based diamine, etc.) for synthesis of polyamide, and then through polymerization reaction. It has the characteristics of green, environment-friendly, renewable raw materials, etc. For example, compared with traditional PA6 and PA66, PA56 uses renewable plant raw materials, reduces 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 DEG C, which is beneficial to two-way stretching; PA56 contains unsaturated hydrogen bonds, retains bioactivity, and has unique Young's modulus value, which provides strong and wear-resistant properties and natural soft touch for the material. However, PA56 has poor acid and alkali resistance, which needs to be improved in aluminum plastic film application.

[0007] In summary, how to develop a low light transmittance, superior punch performance and electrolyte-resistant polyamide film is a technical problem that technicians in the field need to solve. SUMMARY

[0008] In order to overcome the shortcomings of the prior art, the present application provides a bio-based polyamide film for aluminum plastic film packaging and a preparation method thereof, which has low light transmittance, superior punch performance, electrolyte resistance and green environmental protection.

[0009] The bio-based polyamide film for aluminum plastic film packaging provided by the present application comprises a coating layer and a bio-based polyamide substrate layer.

[0010] The bio-based polyamide substrate layer is a three-layer bidirectional stretching bio-based polyamide film, which comprises a first substrate layer, a second substrate layer and a third substrate layer from top to bottom, and the first substrate layer is combined with the coating layer.

[0011] 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 from organic silicon modified acrylic resin, polyurethane microspheres and aziridine crosslinking agent in a mass ratio of 8-10:3-5:0.3-0.5.

[0012] The mass ratio of bio-based PA56 to bio-based PA5X in the first substrate layer is 75-90:10-25;

[0013] The mass ratio of bio-based PA56 to bio-based PA5X in the second substrate layer is 72-89:10-25;

[0014] The mass ratio of bio-based PA56 to bio-based PA5X in the third substrate layer is 75-90:10-25.

[0015] In a preferred embodiment of the present application, the first substrate layer component comprises, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, opening agent 0.1%-1%, and slip agent 0.1%-1%.

[0016] In a preferred embodiment of the present application, the second substrate layer component comprises, by mass percentage: bio-based PA56 72%-89%, bio-based PA5X 10%-25%, and black pigment 1%-3%.

[0017] In a preferred embodiment of the present application, the third substrate layer component comprises, by mass percentage: bio-based PA56 75%-90%, bio-based PA5X 10%-25%, opening agent 0.1%-1%, and slip agent 0.1%-1%.

[0018] In a preferred embodiment of the present application, 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; and the melting point of the bio-based PA5X is 180-200℃.

[0019] In a preferred embodiment of the present application, the black pigment is one or a combination of carbon black, graphene, and organic black pigment.

[0020] In a preferred embodiment of the present application, the opening agent is one or a combination of silica, talc, and acrylic microspheres.

[0021] In a preferred embodiment of the present application, the slip agent is one or a combination of erucic acid amide, oleic acid amide, and ethylene bis-stearamide.

[0022] In a preferred embodiment of the present application, the total thickness of the bio-based polyamide substrate layer is 10-30μm, and the thickness of the coating layer is 0.5-2μm.

[0023] The present application also provides a preparation method of the bio-based polyamide film for aluminum-plastic film packaging as described above, comprising the following steps:

[0024] S1, preparation of an acrylic coating solution:

[0025] 8wt%-10wt% of silicone-modified acrylic resin is dissolved in water, heated and stirred at 60-80℃ until the silicone-modified acrylic resin is completely dissolved, and then cooled to room temperature to obtain an acrylic solution with a concentration of 8wt%-10wt%;

[0026] 0.3wt%-0.5wt% of aziridine crosslinking agent and 3wt%-5wt% of polyurethane microspheres are added into the acrylic acid solution, and stirring and ultrasonic are carried out until the dispersion is uniform, to prepare an acrylic coating solution;

[0027] S2, each component in the first substrate layer, the second substrate layer and the third substrate layer is mixed in a respective proportion, melt blended, extruded, granulated, dried by a twin-screw extruder, to obtain a first master batch, a second master batch and a third master batch, respectively, for standby use; wherein the extrusion temperature of the first master batch, the second master batch and the third master batch is 200-280℃;

[0028] S3, the first master batch obtained in S2 is put into the first extruder to make the first substrate layer; the second master batch is put into the second extruder to make the second substrate layer; and the third master batch 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-shaped die are 220-280℃;

[0029] S4, the first substrate layer, the second substrate layer and the third substrate layer in S3 are extruded, quenched and cast into a sheet, and then MD stretched; wherein the quenching roller temperature is 25-30℃, the MD preheating temperature is 65-85℃, the MD stretching temperature is 60-75℃, and the stretching ratio is 1.8-2.2 times;

[0030] S5, the acrylic coating solution prepared in S1 is coated on the surface of the first substrate layer, and then TD stretched and heat set, to obtain a coated polyamide film for aluminum-plastic film packaging; wherein the TD preheating temperature is 85-105℃, the TD stretching temperature is 80-100℃, the setting temperature is 180-230℃, and the stretching ratio is 2.5-3.2 times.

[0031] The bio-based polyamide film for aluminum-plastic film packaging and the preparation method thereof provided by the application have the following effects compared with the prior art:

[0032] This invention utilizes the high strength, high modulus, and wear-resistant flexibility of bio-based PA56, synergistically adding long-chain bio-based PA5X. On one hand, this reduces the water absorption of bio-based PA56, ensuring the dimensional stability of the film; on the other hand, it toughens the bio-based PA56, improving its impact resistance. Furthermore, bio-based PA56 provides excellent coloring properties for bio-based PA5X, allowing for the addition of a higher content of black pigment. This reduces light transmittance without the need for black matte oil, reducing manufacturing costs and processes. The synergistic use of both, along with an acrylic coating solution, reduces the film's elongation ratio, ensuring both strength and toughness, lowering the coefficient of friction, and improving electrolyte resistance, achieving high dent resistance in the flat film method. Therefore, the bio-based polyamide film for aluminum-plastic film encapsulation of this invention has a simple production process, uses environmentally friendly materials, has low light transmittance, and exhibits excellent overall performance, reducing downstream aluminum-plastic composite film production processes and saving costs. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The layer structure diagram of the thin film of Embodiment 1 provided by the present invention.

[0035] Figure label:

[0036] Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In the description of the present application, it should be noted that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0039] The present application provides the following examples and comparative examples:

[0040] Example 1

[0041] The bio-based polyamide film for aluminum-plastic film packaging of this example 1 comprises a coating layer 10 and a bio-based polyamide substrate layer 20; the bio-based polyamide substrate layer is a three-layer bidirectional stretched bio-based polyamide film, which comprises 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 compounded with the coating layer 10;

[0042] The thickness of the coating layer 10 is 1 μm; the thickness of the bio-based polyamide substrate layer 20 is 25 μm;

[0043] The first substrate layer 21 comprises, by mass percentage: bio-based PA56 89%, bio-based PA512 10%, silicon dioxide 0.5%, and ethylene bis-stearamide 0.5%;

[0044] The second substrate layer 22 comprises, by mass percentage: bio-based PA56 88%, bio-based PA512 10%, and carbon black 2%;

[0045] The third substrate layer 23 comprises, by mass percentage: bio-based PA56 89%, bio-based PA512 10%, silicon dioxide 0.5%, and ethylene bis-stearamide 0.5%;

[0046] The acrylic coating solution is made of silicone-modified acrylic resin, 0.4wt% aziridine crosslinking agent 4wt% polyurethane microspheres and water, and its solid content is 9wt%.

[0047] Example 2

[0048] The bio-based polyamide film for aluminum-plastic film packaging of example 2 has the same structure and layer thickness as example 1, and is different from example 1 in that:

[0049] The first substrate layer 21 component includes, by mass percentage: bio-based PA56 83%, bio-based PA512 15%, silicon dioxide 1%, ethylene bis-stearamide 1%;

[0050] The second substrate layer 22 component includes, by mass percentage: bio-based PA56 88%, bio-based PA512 10%, carbon black 2%;

[0051] The third substrate layer 23 component includes, by mass percentage: bio-based PA56 83%, bio-based PA512 15%, silicon dioxide 1%, ethylene bis-stearamide 1%;

[0052] The acrylic coating solution is made of 10wt% silicone-modified acrylic resin, 0.5wt% aziridine crosslinking agent, 5wt% polyurethane microspheres and water, and its solid content is 10wt%.

[0053] Example 3

[0054] The bio-based polyamide film structure for aluminum-plastic film packaging of this example 3 has the same thickness of each layer as example 1, and differs from example 1 in that:

[0055] The first substrate layer 21 component includes, by mass percentage: bio-based PA56 84.8%, bio-based PA512 15%, silicon dioxide 0.1%, ethylene bis-stearamide 0.1%;

[0056] The second substrate layer 22 component is bio-based PA56 84%, bio-based PA512 15%, carbon black 1%;

[0057] The third substrate layer 23 component includes, by mass percentage: bio-based PA56 84.8%, bio-based PA512 15%, silicon dioxide 0.1%, ethylene bis-stearamide 0.1%;

[0058] The acrylic coating solution is made of 8wt% silicone-modified acrylic resin, 0.3wt% aziridine crosslinking agent 3wt% polyurethane microspheres and water, and its solid content is 8wt%;

[0059] Example 4

[0060] The bio-based polyamide film structure for aluminum-plastic film packaging of this example 4 has the same thickness of each layer as example 1, and differs from example 1 in that:

[0061] The first substrate layer 21 component includes, by mass percentage: bio-based PA56 89%, bio-based PA510 10%, talc 0.5%, erucamide 0.5%;

[0062] The second substrate layer 22 is composed of 88% bio-based PA56, 10% bio-based PA51 and 2% organic black pigment;

[0063] The third substrate layer 23 is composed of 89% bio-based PA56, 10% bio-based PA51, 0.5% talcum powder and 0.5% erucic acid amide according to the mass percentage.

[0064] The acrylic coating solution is made of 9wt% silicone-modified acrylic resin, 0.4wt% aziridine crosslinking agent, 4wt% polyurethane microspheres and water, and the solid content is 9wt%.

[0065] The application also provides a preparation method of the above-mentioned embodiments 1-4, comprising the following steps:

[0066] S1, preparation of the acrylic coating solution:

[0067] 8wt%-10wt% of the silicone-modified acrylic resin is dissolved in water, heated and stirred at 60-80℃ until the silicone-modified acrylic resin is completely dissolved, and then reduced to room temperature to obtain an acrylic solution with a concentration of 8wt%-10wt%;

[0068] 0.3wt%-0.5wt% of the aziridine crosslinking agent and 3wt%-5wt% of the polyurethane microspheres are added to the acrylic solution, and stirred and ultrasonically treated until uniformly dispersed to prepare the acrylic coating solution;

[0069] S2, each component in the first substrate layer 21, the second substrate layer 22 and the third substrate layer 23 is mixed according to the respective proportion, melt blended, extruded, granulated, dried by a double-screw extruder to obtain the first master batch, the second master batch and the third master batch respectively for standby use; wherein the extrusion temperature of the first master batch, the second master batch and the third master batch is 200-280℃;

[0070] S3, the first master batch obtained in S2 is put into the first extruder to make the first substrate layer 21; the second master batch is put into the second extruder to make the second substrate layer 22; and the third master batch 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-shaped die are 220-280℃.

[0071] S4, the first substrate layer 21, the second substrate layer 22 and the third substrate layer 23 in S3 are extruded, rapidly cooled and cast into a sheet, and then MD stretched; wherein the rapid cooling roller temperature is 25-30℃, the MD preheating temperature is 65-85℃, the MD stretching temperature is 60-75℃, and the stretching ratio is 1.8-2.2 times.

[0072] S5, coating the acrylic coating solution prepared in S1 on the surface of the first substrate layer 21, then performing TD stretching, heat setting, thereby obtaining a coated polyamide film for an 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.

[0073] Comparative Example 1

[0074] Comparative Example 1 uses a commonly used biaxially stretched nylon film on the market, with a thickness of 25 μm, and the specific components and proportions are as follows:

[0075] The components of the first substrate layer 21 include PA6 99%, silicon dioxide 0.5%, and erucic acid amide 0.5% by mass percentage;

[0076] The components of the second substrate layer 22 include PA6 100% by mass percentage;

[0077] The components of the third substrate layer 23 include PA6 99%, silicon dioxide 0.5%, and erucic acid amide 0.5% by mass percentage.

[0078] Comparative Example 2

[0079] The coated polyamide film of Comparative Example 2 has a coated layer and a polyamide substrate layer from inside to outside;

[0080] The acrylic coating solution is made of organosilicon modified acrylic resin and water, with a solid content of 9 wt%;

[0081] The polyamide substrate layer is a commonly used biaxially stretched nylon film on the market, with the same components and proportions as Comparative Example 1, and a thickness of 25 μm;

[0082] The preparation method and coating method of the acrylic coating solution are the same as in the example.

[0083] Comparative Example 3

[0084] The coated polyamide film of Comparative Example 3 has a coated layer and a polyamide substrate layer from inside to outside;

[0085] The acrylic coating solution is made of organosilicon modified acrylic resin, 0.4 wt% aziridine crosslinking agent, 4 wt% polyurethane microspheres, and water, with a solid content of 9 wt%;

[0086] The polyamide substrate layer is a commonly used biaxially stretched nylon film on the market, with the same components and proportions as Comparative Example 1, and a thickness of 25 μm;

[0087] The preparation method and coating method of the acrylic coating solution are the same as in the example.

[0088] Comparative Example 4

[0089] The coated polyamide film for aluminum-plastic film packaging of Comparative Example 4 is the same as Example 1 in structure, thickness of each layer, composition and preparation method of acrylic coating solution, preparation method and coating method of polyamide substrate layer, and is different from Example 1 in that:

[0090] The bio-based PA56 component in the first substrate layer, the second substrate layer and the third substrate layer of Example 1 is replaced by PA6, and the extrusion temperature of each layer and the master batch is controlled between 180-240℃.

[0091] Comparative Example 5

[0092] The coated polyamide film for aluminum-plastic film packaging of Comparative Example 5 is the same as Example 1 in structure, thickness of each layer, composition and preparation method of acrylic coating solution, preparation method and coating method of polyamide substrate layer, and is different from Example 1 in that:

[0093] The first substrate layer component includes, by mass percentage: bio-based PA56 99%, silicon dioxide 0.5%, ethylene bis-stearamide 0.5%;

[0094] The second substrate layer component includes, by mass percentage: bio-based PA56 98%, carbon black 2%;

[0095] The third substrate layer component includes, by mass percentage: bio-based PA56 99%, silicon dioxide 0.5%, ethylene bis-stearamide 0.5%.

[0096] Comparative Example 6

[0097] The coated polyamide film for aluminum-plastic film packaging of Comparative Example 6 is the same as Example 1 in structure, thickness of each layer, composition and preparation method of acrylic coating solution, preparation method and coating method of polyamide substrate layer, and is different from Example 1 in that:

[0098] The first substrate layer component includes, by mass percentage: bio-based PA56 94%, bio-based PA512 5%, silicon dioxide 0.5%, ethylene bis-stearamide 0.5%;

[0099] The second substrate layer component is bio-based PA56 93%, bio-based PA512 5%, carbon black 2%;

[0100] The third substrate layer component includes, by mass percentage: bio-based PA56 94%, bio-based PA512 5%, silicon dioxide 0.5%, ethylene bis-stearamide 0.5%.

[0101] The films prepared in the examples and comparative examples are tested for performance, and the specific test method is:

[0102] Thickness: tested according to GB / T 20220-2006 "Plastics - Determination of average thickness, roll average thickness and mass per area of film and sheet specimens";

[0103] Haze and light transmittance: tested according to GB / T 2410-2008 "Standard test methods for haze and luminous transmittance of transparent plastics";

[0104] Friction coefficient: tested according to GB / T 10006-1988 "Determination of the coefficient of friction of plastics film and sheet";

[0105] Tensile strength and elongation at break: tested according to GB / T 1040-3 "Determination of tensile properties of plastics - Part 3: test conditions for film and sheet";

[0106] Punching depth test: the polyamide film of the examples and the comparative examples was prepared into PA / AL / CPP composite film, and a punching mold used by a lithium ion battery aluminum plastic packaging film factory was used to clamp the PA / AL / CPP composite film, and different depth of the punching head was used to test the film until the film was punched through;

[0107] Electrolyte resistance test: commercially available lithium battery electrolyte was dropped on the surface of the biaxially oriented polyamide film prepared in the above examples and the film in the comparative examples, and after being placed at 25°C RH50% for 2h, the electrolyte was wiped off with paper, and the surface corrosion was observed. The electrolyte corrosion resistance is represented by "O", and the electrolyte corrosion resistance is represented by "△".

[0108] The test results are shown in Table 1:

[0109] Table 1

[0110]

[0111] As shown in Table 1, compared with Comparative Example 1 which only uses a commonly used biaxially stretched nylon film on the market, the film provided by Examples 1-4 has 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 punching depth and electrolyte resistance are improved;

[0112] The acrylic coating solution of the coating layer of Comparative Example 2 does not add polyurethane microspheres and aziridine crosslinking agent, and the substrate layer uses a commonly used biaxially stretched nylon film on the market. Compared with Comparative Example 2, the film provided by Examples 1-4 has 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;

[0113] The coating layer of the comparative example 3 uses the acrylic coating solution prepared by the present application, and the substrate layer uses the biaxially stretched nylon film commonly used in the market. Compared with the comparative example 3, the tensile strength and the ductility of the film provided by the examples 1-4 are significantly improved, and the light transmittance is reduced. After being compounded with aluminum foil and PE, the pit depth is improved;

[0114] The coating layer of the comparative example 4 uses the acrylic coating solution prepared by the present application, and the substrate layer uses PA6 components. Compared with the comparative example 4, the tensile strength of the film provided by the examples 1-4 is improved, and after being compounded with aluminum foil and PE, the pit depth is improved;

[0115] The coating layer of the comparative example 5 uses the acrylic coating solution prepared by the present application, and the substrate layer components are not added with bio-based PA512. Compared with the comparative example 5, the pit depth of the film provided by the examples 1-4 is improved after being compounded with aluminum foil and PE;

[0116] The coating layer of the comparative example 6 uses the acrylic coating solution prepared by the present application, and the substrate layer component ratio is changed. Compared with the comparative example 6, the pit depth of the film provided by the examples 1-4 is improved after being compounded with aluminum foil and PE;

[0117] In summary, the bio-based polyamide film for aluminum-plastic film packaging of the present application has high tensile strength and ductility, indicating that it has good reliability and durability, small friction coefficient, low gloss, good light shielding performance, and after being compounded with aluminum foil and PE, it has good pit performance and good electrolyte resistance. The material is green and environmentally friendly, and is particularly suitable for aluminum-plastic composite film soft packaging.

[0118] Although terms such as bio-based polyamide film, substrate layer, coating layer, and acrylic coating solution are used more frequently in this document, the possibility of using other terms is not excluded. The use of these terms is only to facilitate the description and explanation of the essence of the present application; any additional limitation is contrary to the spirit of the present application.

[0119] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A bio-based polyamide film for use in an aluminum laminate packaging, characterized by: The coating layer and the bio-based polyamide substrate layer are combined; The bio-based polyamide substrate layer is a three-layer biaxially stretched bio-based polyamide film, which comprises a first substrate layer, a second substrate layer and a third substrate layer from top to bottom, and the first substrate layer is combined with the coating layer; The coating layer is formed by coating an acrylic coating solution on the surface of the bio-based polyamide substrate layer, and the acrylic coating solution is prepared from 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; The first substrate layer comprises bio-based PA56 75%-90%, bio-based PA5X 10%-25%, opening agent 0.1%-1%, and slip agent 0.1%-1% by mass percentage; The second substrate layer comprises bio-based PA56 72%-89%, bio-based PA5X 10%-25%, and black pigment 1%-3% by mass percentage; The third substrate layer comprises bio-based PA56 75%-90%, bio-based PA5X 10%-25%, opening agent 0.1%-1%, and slip agent 0.1%-1% by mass percentage; 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, and the melting point of the bio-based PA5X is 180-200℃.

2. The bio-based polyamide film for an aluminum laminate packaging according to claim 1, characterized by: The black pigment is one or a combination of carbon black, graphene, and organic black pigment.

3. The bio-based polyamide film for an aluminum laminate packaging according to claim 1, characterized by: The opening agent is one or a combination of silicon dioxide, talc, and acrylic microspheres.

4. The bio-based polyamide film for an aluminum laminate packaging according to claim 1, characterized by: The slip agent is one or a combination of erucic acid amide, oleic acid amide, and ethylene bis-stearamide.

5. The bio-based polyamide film for an aluminum laminate packaging according to claim 1, characterized by: The total thickness of the bio-based polyamide substrate layer is 10-30μm, and the thickness of the coating layer is 0.5-2μm.

6. A process for the preparation of a bio-based polyamide film for lamination to an aluminum foil as claimed in any one of claims 1 to 5, characterized in that The method comprises the following steps: S1, preparation of the acrylic coating solution: 8wt%-10wt% of silicone-modified acrylic resin is dissolved in water, heated and stirred at 60-80℃ until the silicone-modified acrylic resin is completely dissolved, and then cooled to room temperature to obtain an acrylic solution with a concentration of 8wt%-10wt%; 0.3wt%-0.5wt% of aziridine crosslinking agent and 3wt%-5wt% of polyurethane microspheres are added to the acrylic solution, stirred and ultrasonicated until uniformly dispersed, to prepare the acrylic coating solution; S2, each component in the first substrate layer, the second substrate layer and the third substrate layer is mixed in a respective proportion, melt blended, extruded, granulated by a twin-screw extruder, dried, to obtain a first master batch, a second master batch and a third master batch respectively, for standby use; wherein the extrusion temperature of the first master batch, the second master batch and the third master batch is 200-280℃; S3, the first master batch obtained in S2 is put into a first extruder to make the first substrate layer; the second master batch is put into a second extruder to make the second substrate layer; the third master batch is put into a 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℃; S4, the first substrate layer, the second substrate layer and the third substrate layer in S3 are extruded, quenched and cast into a sheet, and then MD stretched; wherein the quenching roller temperature is 25-30℃, the MD preheating temperature is 65-85℃, the MD stretching temperature is 60-75℃, 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, and then TD stretched, heat set, to obtain a coated polyamide film for aluminum-plastic film packaging; wherein the TD preheating temperature is 85-105℃, the TD stretching temperature is 80-100℃, the setting temperature is 180-230℃, and the stretching ratio is 2.5-3.2 times.

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