PP / PA film preparation method based on PA-PP co-extrusion film blowing technology

Abstract

The invention relates to the technical field of nylon co-extrusion film blowing, and particularly discloses a PP / PA film preparation method based on a PA-PP co-extrusion film blowing technology, which comprises the following steps: respectively melting and plasticizing a PP layer raw material and a PA layer raw material, extruding, blowing the film, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the raw materials of the PP layer is 160-180 DEG C, and the melting and plasticizing temperature of the raw materials of the PA layer is 220-240 DEG C. Compared with a PP film and a PA film, the blown film disclosed by the invention not only has stronger barrier capacity and puncture resistance, but also has the characteristics of stronger moisture resistance, quality guarantee and fresh keeping, is long in shelf life, is convenient to operate and control, simplifies the production process, is high in production efficiency, and can be industrially produced on a large scale.

Description

Technical Field

[0001] The invention relates to the technical field of nylon co-extrusion blown film, and in particular to a method for preparing a PP / PA film based on the PA-PP co-extrusion blown film technology. Background Art

[0002] The packaging industry is the largest consumer market for plastics, accounting for about 40.1% of the total plastics, of which composite films account for about 20% of packaging films, and most of the composite films are nylon / polyethylene (PA / PP) composite films.

[0003] Nylon (PA) has good mechanical properties and chemical stability, and has excellent wear resistance, heat resistance and chemical resistance, but it has the defects of low melt viscosity, poor impact resistance and strong water absorption.

[0004] Polypropylene (PP) is a thermoplastic synthetic resin with excellent performance. It is a colorless, translucent, thermoplastic, lightweight general-purpose plastic with chemical resistance, heat resistance, electrical insulation, high-strength mechanical properties and good high-wear resistance processing performance. Therefore, PA and PP are co-extruded into blown film to achieve complementary performance and improve the comprehensive performance of the material, thereby expanding the scope of application.

[0005] PA / PP composite film can complement each other's strengths and weaknesses, combining the chemical stability and barrier properties of nylon. It is widely used in food packaging, industrial product packaging, daily chemical product packaging and other industries.

[0006] However, PA is a polar polymer, while PP is a non-polar polymer. The two have different thermal properties and rheological mismatch, which can easily lead to new problems due to different melting, freezing and shrinkage ratios between layers, especially the barrier and impact toughness of the composite film cannot be guaranteed. Therefore, how to solve the rheological mismatch phenomenon while ensuring the barrier performance and strength of the material has become a technical problem that needs to be solved at present. Summary of the invention

[0007] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a PP / PA film preparation method based on PA-PP co-extrusion blown film technology.

[0008] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps: melting and plasticizing a PP layer raw material and a PA layer raw material respectively, extruding and blowing a film, wherein the blowing ratio is 1:2-4, the film blowing temperature is 200-240°C, and cooling to obtain a PP / PA film; wherein the temperature for melting and plasticizing the PP layer raw material is 160-180°C, and the temperature for melting and plasticizing the PA layer raw material is 220-240°C.

[0009] Preferably, the raw materials of the PP layer include, by mass, 50-100 parts of homopolypropylene, 1-5 parts of EPDM rubber, 1-2 parts of antistatic agent, 1-2 parts of polyethylene wax, 1-2 parts of maleic anhydride, and 0.01-0.1 parts of initiator a.

[0010] Preferably, the initiator a is dibenzoyl peroxide.

[0011] Preferably, the PP layer raw material is obtained by the following specific steps: adding polyethylene wax and maleic anhydride to xylene, stirring at 70-90° C. for 10-20 min, adding initiator a, continuing stirring for 1-2 h, filtering, washing with acetone, drying, crushing, adding homopolymer polypropylene, EPDM rubber, and antistatic agent and mixing evenly.

[0012] Preferably, the raw materials of the PA layer include, by mass: 40-100 parts of nylon 6, 1-5 parts of amino-terminated polyamidoamine, 1-2 parts of dispersant, 1-3 parts of EPDM rubber, 0.1-1 parts of maleic anhydride, and 0.01-0.1 parts of initiator b.

[0013] Preferably, the PA layer raw material is obtained by the following specific steps: EPDM rubber and initiator b are mixed, the temperature is adjusted to 70-80°C for 1-2h, maleic anhydride is added, and blended at 180-210°C for 1-5min, and nylon 6, amino-terminated polyamide amine and dispersant are added thereto and mixed for 10-30min.

[0014] Preferably, the initiator b is dicumyl peroxide.

[0015] Preferably, the amino-terminated polyamidoamine is a second-generation dendritic polyamidoamine.

[0016] Preferably, the amino-terminated polyamidoamine is an activated amino-terminated polyamidoamine; the activated amino-terminated polyamidoamine is obtained by the following specific steps: adding amino-terminated polyamidoamine and oxalic acid to water and stirring for 10-30 minutes, adding mica powder thereto under stirring, stirring at 40-50° C. for 1-2 hours, heating to 70-80° C. and continuing stirring for 2-4 hours, cooling to room temperature, centrifuging, washing the precipitate with water, and vacuum drying.

[0017] The terminal amino group of amino-terminated polyamidoamine carries a large amount of positive charge under the action of oxalic acid, which can be exchanged with the exchangeable cations between the mica powder crystal layers and inserted into the interlayer gaps, which not only weakens the interlayer force of mica, but also makes it easier for the mica powder to be fully dispersed and combined in PA due to the polyamidoamine structure between the layers.

[0018] Preferably, the mass ratio of the amino-terminated polyamidoamine, oxalic acid and mica powder is 1-5:1-3:10-15.

[0019] Beneficial effects:

[0020] EPDM rubber has a low glass transition temperature. Under the action of maleic anhydride, the polarity of EPDM rubber can be effectively enhanced, which not only solves the problem of poor compatibility with PA, but also effectively enhances the flexibility of PA molecular chains. Further combined with activated amino-terminated polyamide amine, the amino-terminated polyamide amine can be evenly dispersed in PA, which not only makes PA insensitive to temperature and improves its fluidity, but also combines with the carboxyl groups on the surface of maleic anhydride. The dendritic cross-linked network structure fully dispersed in the system cooperates with the lamellar structure of mica, which ensures excellent puncture resistance while ensuring barrier properties, and effectively avoids the adverse effects of the addition of plasticizers on the processing rheological properties of PA.

[0021] The invention adopts maleic anhydride to treat the surface of polyethylene wax, which can effectively enhance the interface compatibility between linear low-density polyethylene and ethylene propylene diene monomer rubber, and the interface bonding strength is high; the raw material of the PA layer and the raw material of the PP layer are respectively added into the extruders of each layer for melting and plasticization, the PA layer and the PP layer can not only complement each other, but also effectively overcome the problems caused by different melting, freezing and shrinkage ratios between the two layers, improve the puncture resistance, and obtain balanced physical and mechanical properties; and make the barrier property of the obtained PP / PA film excellent.

[0022] The blown film of the present invention not only has stronger barrier capacity and puncture resistance than PP film and PA film, but also has the characteristics of strong moisture resistance, quality preservation and freshness preservation, and a long shelf life. Its mechanical properties and oxygen barrier properties all exceed national inspection standards.

[0023] The invention has not only simple production process and convenient operation and control, but also low processing cost, simplified production process, stable quality, high production efficiency and can be used for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a comparison chart of the tensile strength and elongation at break of the PP / PA films obtained in Example 5, Example 6 and the comparative example.

[0025] Figure 2 It is a comparison chart of the puncture resistance and dart impact strength of the PP / PA films obtained in Example 5, Example 6 and the comparative example.

[0026] Figure 3 It is a comparison chart of water vapor permeability and oxygen permeability of PP / PA films obtained in Example 5, Example 6 and the comparative example. DETAILED DESCRIPTION

[0027] The present invention will be further explained below in conjunction with specific embodiments.

[0028] Example 1

[0029] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0030] (1) Add 1 kg of polyethylene wax and 1 kg of maleic anhydride to 10 kg of xylene, stir at 70°C for 10 min, add 0.01 kg of dibenzoyl peroxide, continue stirring for 1 h, and the stirring speed is 1000 r / min. Filter, wash with acetone, dry, and crush. Add 50 kg of homopolypropylene, 1 kg of EPDM rubber, and 1 kg of antistatic agent and mix well to obtain the PP layer raw material.

[0031] (2) 1 kg of EPDM rubber and 0.01 kg of diisopropylbenzene peroxide were added to a rotary evaporator and treated at 70°C for 1 h. 0.1 kg of maleic anhydride was added and blended at 180°C for 1 min. 40 kg of PA6, 1 kg of second-generation amino-terminated polyamidoamine and 1 kg of dispersant were added thereto and mixed at a speed of 20 r / min for 10 min to obtain a PA layer raw material.

[0032] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:2, the film blowing temperature is 200°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 160°C, and the melting and plasticizing temperature of the PA layer raw material is 220°C.

[0033] Example 2

[0034] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0035] (1) Add 2 kg of polyethylene wax and 2 kg of maleic anhydride to 30 kg of xylene, stir at 90 °C for 20 min, add 0.1 kg of dibenzoyl peroxide, continue stirring for 2 h, and the stirring speed is 2000 r / min. Filter, wash with acetone, dry, and crush. Add 100 kg of homopolypropylene, 5 kg of EPDM rubber, and 2 kg of antistatic agent and mix well to obtain PP layer raw materials.

[0036] (2) 3 kg of EPDM rubber and 0.1 kg of diisopropylbenzene peroxide were added to a rotary evaporator and treated at 80° C. for 2 h. 1 kg of maleic anhydride was added and blended at 210° C. for 5 min. 100 kg of PA6, 5 kg of second-generation amino-terminated polyamide amine and 2 kg of dispersant were added thereto and mixed at a speed of 60 r / min for 30 min to obtain a PA layer raw material.

[0037] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:4, the film blowing temperature is 240°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 180°C, and the melting and plasticizing temperature of the PA layer raw material is 240°C.

[0038] Example 3

[0039] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0040] (1) 1.3 kg of polyethylene wax and 1.8 kg of maleic anhydride were added to 15 kg of xylene, stirred at 85 ° C for 12 min, 0.07 kg of dibenzoyl peroxide was added, and stirring was continued for 80 min at a stirring speed of 1800 r / min. The mixture was filtered, washed with acetone, dried, and crushed. 70 kg of homopolypropylene, 4 kg of EPDM rubber, and 1.3 kg of antistatic agent were added and mixed uniformly to obtain a PP layer raw material.

[0041] (2) 5 kg of second-generation amino-terminated polyamidoamine and 1 kg of oxalic acid were added to 60 kg of water, stirred at a speed of 500 r / min for 30 min, 10 kg of mica powder was added thereto under stirring, stirred at a temperature of 50° C. for 1 h, heated to 80° C. and continued to stir for 2 h, cooled to room temperature, centrifuged, and the precipitate was washed with deionized water and vacuum dried to obtain an activated amino-terminated polyamidoamine;

[0042] 2.5 kg of EPDM rubber and 0.03 kg of dicumyl peroxide were added to a rotary evaporator, treated at 77°C for 80 min, 0.8 kg of maleic anhydride was added, and blended at 190°C for 4 min. 60 kg of PA6, 4 kg of activated terminal amino polyamide amine, and 1.3 kg of dispersant were added thereto, and mixed at a speed of 50 r / min for 15 min to obtain a PA layer raw material.

[0043] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:3.5, the film blowing temperature is 225°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 175°C, and the melting and plasticizing temperature of the PA layer raw material is 225°C.

[0044] Example 4

[0045] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0046] (1) 1.7 kg of polyethylene wax and 1.2 kg of maleic anhydride were added to 25 kg of xylene, stirred at 75 ° C for 18 min, 0.03 kg of dibenzoyl peroxide was added, and stirring was continued for 100 min at a stirring speed of 1200 r / min. The mixture was filtered, washed with acetone, dried, and crushed. 90 kg of homopolypropylene, 2 kg of EPDM rubber, and 1.7 kg of antistatic agent were added and mixed uniformly to obtain a PP layer raw material.

[0047] (2) 1 kg of the second generation amino-terminated polyamidoamine and 3 kg of oxalic acid were added to 30 kg of water, stirred at a speed of 1200 r / min for 10 min, 15 kg of mica powder was added thereto under stirring, stirred at a temperature of 40° C. for 2 h, heated to 70° C. and continued to stir for 4 h, cooled to room temperature, centrifuged, and the precipitate was washed with deionized water and vacuum dried to obtain an activated amino-terminated polyamidoamine;

[0048] 1.5 kg of EPDM rubber and 0.07 kg of dicumyl peroxide were added to a rotary evaporator, treated at 73°C for 100 min, 0.2 kg of maleic anhydride was added, and blended at 200°C for 2 min. 80 kg of PA6, 2 kg of activated terminal amino polyamide amine, and 1.7 kg of dispersant were added thereto, and mixed at 30 r / min for 25 min to obtain a PA layer raw material.

[0049] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:2.5, the film blowing temperature is 225°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 165°C, and the melting and plasticizing temperature of the PA layer raw material is 235°C.

[0050] Example 5

[0051] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0052] (1) 1.5 kg of polyethylene wax and 1.5 kg of maleic anhydride were added to 20 kg of xylene, stirred at 80 ° C for 15 min, 0.05 kg of dibenzoyl peroxide was added, and stirring was continued for 90 min at a stirring speed of 1500 r / min. The mixture was filtered, washed with acetone, dried, and crushed. 80 kg of homopolypropylene, 3 kg of EPDM rubber, and 1.5 kg of antistatic agent were added and mixed uniformly to obtain a PP layer raw material.

[0053] (2) 2 kg of EPDM rubber and 0.05 kg of diisopropylbenzene peroxide were added to a rotary evaporator, treated at 75 °C for 90 min, 0.5 kg of maleic anhydride was added, and the mixture was blended at 195 °C for 3 min. 70 kg of PA6, 3 kg of second-generation amino-terminated polyamidoamine, and 1.5 kg of a dispersant were added thereto, and the mixture was mixed at 40 r / min for 20 min to obtain a PA layer raw material.

[0054] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:3, the film blowing temperature is 225°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 170°C, and the melting and plasticizing temperature of the PA layer raw material is 230°C.

[0055] Example 6

[0056] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0057] (1) 1.5 kg of polyethylene wax and 1.5 kg of maleic anhydride were added to 20 kg of xylene, stirred at 80 ° C for 15 min, 0.05 kg of dibenzoyl peroxide was added, and stirring was continued for 90 min at a stirring speed of 1500 r / min. The mixture was filtered, washed with acetone, dried, and crushed. 80 kg of homopolypropylene, 3 kg of EPDM rubber, and 1.5 kg of antistatic agent were added and mixed uniformly to obtain a PP layer raw material.

[0058] (2) 3 kg of second-generation amino-terminated polyamidoamine and 2 kg of oxalic acid were added to 45 kg of water, stirred at a speed of 800 r / min for 20 min, 12 kg of mica powder was added thereto under stirring, stirred at a temperature of 45° C. for 1.5 h, heated to 75° C. and continued to stir for 3 h, cooled to room temperature, centrifuged, and the precipitate was washed with deionized water and vacuum dried to obtain an activated amino-terminated polyamidoamine;

[0059] 2kg of EPDM rubber and 0.05kg of dicumyl peroxide were added to a rotary evaporator, treated at 75°C for 90min, 0.5kg of maleic anhydride was added, and blended at 195°C for 3min, 70kg of PA6, 2-4kg of activated terminal amino polyamide amine, and 1.5kg of dispersant were added thereto, and mixed at 40r / min for 20min to obtain the PA layer raw material.

[0060] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:3, the film blowing temperature is 225°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 170°C, and the melting and plasticizing temperature of the PA layer raw material is 230°C.

[0061] Comparative Example

[0062] A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology comprises the following steps:

[0063] (1) 1.5 kg of polyethylene wax, 80 kg of homopolymer polypropylene, 3 kg of ethylene propylene diene monomer rubber, and 1.5 kg of antistatic agent are mixed uniformly to obtain a PP layer raw material.

[0064] (2) 3 kg of second-generation amino-terminated polyamidoamine and 2 kg of oxalic acid were added to 45 kg of water, stirred at a speed of 800 r / min for 20 min, 12 kg of mica powder was added thereto under stirring, stirred at a temperature of 45° C. for 1.5 h, heated to 75° C. and continued to stir for 3 h, cooled to room temperature, centrifuged, and the precipitate was washed with deionized water and vacuum dried to obtain an activated amino-terminated polyamidoamine;

[0065] 2 kg of EPDM rubber and 0.05 kg of dicumyl peroxide were added to a rotary evaporator, treated at 75 ° C for 90 min, 0.5 kg of maleic anhydride was added, and blended at 195 ° C for 3 min. 70 kg of PA6, 3 kg of activated terminal amino polyamide amine, and 1.5 kg of dispersant were added thereto, and mixed at a speed of 40 r / min for 20 min to obtain the PA layer raw material.

[0066] (3) Melting and plasticizing the PP layer raw material and the PA layer raw material respectively, extruding and blowing the film, wherein the blowing ratio is 1:3, the film blowing temperature is 225°C, and cooling to obtain a PP / PA film; wherein the melting and plasticizing temperature of the PP layer raw material is 170°C, and the melting and plasticizing temperature of the PA layer raw material is 230°C.

[0067] The thickness of the PP / PA films obtained in Example 5, Example 6 and the comparative example was measured. The thickness of the three films was within the range of 75.0±8.8 μm.

[0068] The PP / PA films obtained in Example 5, Example 6 and the comparative example were tested for mechanical properties. The tensile strength and elongation at break were tested with reference to GB / T 1040.3-2006 "Determination of tensile properties of plastics Part 3 Test conditions for films / sheets", and the tensile speed was 50 mm / min. The puncture resistance of the three was tested with reference to GB / T 37841-2019 "Test method for puncture resistance of plastic films and sheets". The dart impact strength test was performed with reference to Method A in GB / T 9639.1-2008 "Test method for impact resistance of plastic films and sheets - free falling dart method - Part 1: ladder method".

[0069] like Figure 1 and Figure 2 As shown, the tensile strength, puncture resistance and impact strength of the PP / PA film obtained in Example 6 are the highest.

[0070] The water vapor permeability test was carried out according to the weight gain method in GB / T 1037-2021 "Determination of Water Vapor Permeability of Plastic Film and Sheeting - Cup Weight Gain and Weight Loss Method". The test temperature was 38°C, the humidity was 90% RH, the preheating time was 2h, the rotation interval was 10min, and 3 parallels were set for each group.

[0071] Refer to GB / T 1038.1-2022 "Plastic film and sheet gas permeability test method Part 1: Differential pressure method" for oxygen permeability test, the test temperature is 23℃, the humidity is 50%RH, and the vacuum time is 4h. Ensure that the sample surface is free of pollution and scratches, and set 3 parallels for each group.

[0072] like Figure 3 As shown, the barrier properties of the PP / PA film obtained in Example 6 are the best.

[0073] The applicant believes that this is because the present invention uses maleic anhydride to enhance the polarity of EPDM rubber, which not only solves the problem of poor compatibility with PA, but also effectively enhances the flexibility of PA molecular chains, and further cooperates with activated amino-terminated polyamide amine to make the amino-terminated polyamide amine dispersed uniformly in PA, which not only makes PA insensitive to temperature and improves its fluidity, but also can combine with the carboxyl groups on the surface of maleic anhydride, and the dendritic cross-linked network structure fully dispersed in the system cooperates with the sheet structure of mica, while ensuring the barrier performance, the puncture resistance is excellent. The present invention also uses maleic anhydride to treat the surface of polyethylene wax, which can effectively enhance the interface compatibility between linear low-density polyethylene and EPDM rubber, and the interface bonding strength is high. The PA layer raw material and the PP layer raw material are added to the extruders of each layer for melt plasticization. The PA layer and the PP layer can not only complement each other, but also effectively overcome the problems caused by the different melting, freezing and shrinkage ratios between the two layers, improve the puncture resistance, and obtain balanced physical and mechanical properties; and make the barrier performance of the obtained PP / PA film excellent.

[0074] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a PP / PA film based on PA-PP co-extrusion blown film technology, characterized in that: The process comprises the following steps: melting and plasticizing the PP layer raw material and the PA layer raw material respectively, blowing the film after extrusion, and cooling to obtain the PP / PA film; The raw materials of the PP layer include, by mass: 50-100 parts of homopolypropylene, 1-5 parts of EPDM rubber, 1-2 parts of antistatic agent, 1-2 parts of polyethylene wax, 1-2 parts of maleic anhydride, and 0.01-0.1 parts of initiator a; The raw materials of the PA layer include, by mass: 40-100 parts of nylon 6, 1-5 parts of amino-terminated polyamidoamine, 1-2 parts of dispersant, 1-3 parts of EPDM rubber, 0.1-1 parts of maleic anhydride, and 0.01-0.1 parts of initiator B.

2. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 1, characterized in that: Initiator a is dibenzoyl peroxide.

3. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 2, characterized in that: The PP layer raw material is obtained by the following specific steps: adding polyethylene wax and maleic anhydride to xylene, stirring at 70-90° C. for 10-20 minutes, adding initiator a, continuing stirring for 1-2 hours, filtering, washing with acetone, drying, crushing, adding homopolymer polypropylene, EPDM rubber, and antistatic agent and mixing evenly.

4. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 1, characterized in that: Initiator b is dicumyl peroxide.

5. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 4, characterized in that: The PA layer raw material is obtained by the following specific steps: EPDM rubber and initiator b are mixed, the temperature is adjusted to 70-80°C for 1-2h, maleic anhydride is added, and blending is carried out at 180-210°C for 1-5min, and nylon 6, amino-terminated polyamide amine and dispersant are added thereto and mixed for 10-30min.

6. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 1, characterized in that: The amino-terminated polyamidoamine is a second-generation dendritic polyamidoamine.

7. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 6, characterized in that: The amino-terminated polyamidoamine is an activated amino-terminated polyamidoamine; the activated amino-terminated polyamidoamine is obtained by the following specific steps: adding amino-terminated polyamidoamine and oxalic acid into water and stirring for 10-30 minutes, adding mica powder thereto under stirring, stirring at 40-50° C. for 1-2 hours, heating to 70-80° C. and continuing stirring for 2-4 hours, cooling to room temperature, centrifuging, washing the precipitate with water, and vacuum drying.

8. The method for preparing PP / PA film based on PA-PP co-extrusion blown film technology according to claim 7, characterized in that: The mass ratio of amino-terminated polyamidoamine, oxalic acid and mica powder is 1-5:1-3:10-15.

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