Modified moisture absorption composite film and preparation method thereof

Abstract

The invention belongs to the technical field of aluminum-plastic composite films, and particularly provides a modified moisture absorption composite film and a preparation method thereof.The preparation method comprises the following steps that a PET film, Al foil and a modified PE film are coated and compounded according to the stacking sequence from outside to inside, then curing and drying are conducted, and the modified moisture absorption composite film is obtained; the preparation method of the modified PE film comprises the following steps: taking polyethylene master batch and modified zeolite, mixing, and then carrying out extrusion and film blowing treatment, thereby obtaining the modified PE film. The preparation method of the modified zeolite comprises the following steps: taking calcined kaolin, seed crystal and sodium carbonate, mixing and grinding, adding water for dispersion, adjusting the silica-alumina ratio to 3.3-3.5, standing for aging, then heating for crystallization treatment, drying the product, and sieving to obtain the modified zeolite. The modified zeolite prepared in the invention is added into a PE base material, and a modified PE film obtained after film blowing molding has good hygroscopicity and antibacterial property.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum-plastic composite film, and particularly relates to a modified moisture-absorbing composite film and a preparation method thereof. BACKGROUND

[0002] The aluminum-plastic composite film is a kind of multi-layer flexible packaging material. Compared with the traditional single-layer plastic film, the aluminum-plastic composite film can effectively block oxygen, water vapor, light and other external factors through the synergistic effect of the multi-layer structure, thereby significantly prolonging the shelf life of the content. The aluminum-plastic composite film combines the flexibility, printability of plastic and the high barrier property of aluminum foil, and has obvious advantages in food packaging, medicines, electronic components and the like.

[0003] The aluminum-plastic composite film is mainly composed of a printing layer, a barrier layer (aluminum foil) and a heat-sealing layer which are compounded by an adhesive. The heat-sealing layer is usually polyethylene (PE) or cast polypropylene (CPP). Compared with CPP, PE has more excellent heat adhesion, low-temperature heat-sealing property and flexibility, and has a lower cost, which is suitable for large-scale production. Although PE performs well in the heat-sealing layer, it has the defect of poor moisture absorption. The products (such as moisture-sensitive medicines or electronic components) packaged by PE are easily damaged in a high-temperature and high-humidity environment. In order to improve the moisture absorption, the industry usually adds a moisture-absorbing component, such as zeolite molecular sieve, to PE to reduce the humidity inside the package through physical adsorption. However, the zeolite molecular sieve is an inorganic material, and has poor compatibility with the PE organic matrix. The prepared film product is prone to perforation, damage and other problems, which seriously affects the packaging effect.

[0004] The patent application file with the application publication number CN112757735A discloses an antibacterial easy-to-peel moisture-absorbing PE film, a preparation method and a packaging structure. The PE film body includes an outer printing / composite layer, a moisture-absorbing layer and an antibacterial easy-to-peel layer. Zeolite molecular sieve is used as a moisture-absorbing agent in the moisture-absorbing layer to provide a moisture-proof and moisture-absorbing function for the packaging content. In combination with the modified nano-ZnO inorganic antibacterial agent in the antibacterial easy-to-peel layer, the moisture absorption and antibacterial properties of the PE film are comprehensively improved.

[0005] In the above scheme, although a PE film with antibacterial and moisture-absorbing properties is prepared by a multi-layer composite form, the multi-layer composite form will inevitably increase the thickness of the PE film. When the film is used for coating with Al foil, the thickness of the aluminum-plastic film will be further increased. Moreover, since the modified nano-ZnO antibacterial agent is embedded in the PE system through melt blending in the antibacterial easy-to-peel layer and directly contacts the packaging content, the precipitation and phase separation problems will be aggravated. Therefore, it is necessary to find a modified moisture-absorbing film with moisture absorption, antibacterial properties and reduced precipitation of antibacterial active metal ions and a preparation method thereof. SUMMARY

[0006] In order to further inhibit the antibacterial group and improve the compatibility of inorganic moisture-absorbing components and PE base material, the application provides a modified moisture-absorbing composite film and a preparation method thereof.

[0007] The application first provides a preparation method of a modified moisture-absorbing composite film, and the preparation steps include the following: According to the folding sequence from outside to inside, the PET film, the Al foil and the modified PE film are coated and combined, and then matured and dried to obtain the modified moisture-absorbing composite film. The preparation steps of the modified PE film include the following: The polyethylene master batch and the modified zeolite are mixed, and then extruded and blown into a film to obtain the modified PE film. The preparation steps of the modified zeolite include the following: The calcined kaolin, the seed crystal and sodium carbonate are mixed and ground, dispersed with water, and adjusted to a silicon-aluminum ratio of 3.3-3.5, placed and aged, and then subjected to temperature crystallization treatment, and the product is dried, crushed and sieved to obtain the modified zeolite. The mass ratio of the calcined kaolin, the seed crystal and sodium carbonate is (40-60):(1-2):(6-8); the temperature crystallization treatment is adjusted to a temperature of 120-150℃ for 15-18h; The seed crystal is obtained by grafting reaction of methyl methacrylate, glycidyl methacrylate and polyethylene imine after microemulsion polymerization and PE-g-MAH; The coating and combining operation is controlled to a sizing amount of 20±2g / m 2 ; The mass ratio of the polyethylene master batch and the modified zeolite is (120-150):(5-8); The extrusion and film blowing treatment is set to a cylinder zone temperature of 150-165℃, a die temperature of 150-155℃, and a blow ratio of (2-2.5):1; The thickness of the modified PE film is 50-55 microns.

[0008] By adopting the technical scheme, the modified zeolite is mixed in the PE base material during the melting process, the antibacterial property of the PE blown film is improved, and the compatibility problem of the inorganic component and the base material is reduced; the modified zeolite takes the silicon-rich aluminum sol solution as a precursor, is mixed with seeds, and is subjected to hydrothermal crystallization; in the seed preparation process, the elastomer is obtained after the polymerization of the organic monomer microemulsion, the introduced polyethylene imine organic amine chain segment can strengthen the template effect of the seed, and in the immersion treatment process, the divalent copper ions and the divalent zinc ions in the immersion solution are chelated by virtue of the amine group structure of the molecular chain segment, the silicon-rich aluminum sol takes the elastomer as a core during the subsequent hydrothermal crystallization of the zeolite, and the chelated metal ions are embedded in the zeolite framework, so that the migration of the metal ions from the zeolite system is inhibited; the elastomer is subjected to graft modification of long-chain PE-g-MAH, the long-chain nonpolar chain segment is introduced on the surface of the elastomer, the nonpolar grafted PE chain segment exposed on the surface of the zeolite crystallization product after crushing has high compatibility with the base material, and the influence of phase separation on the film product can be reduced through molecular chain entanglement.

[0009] Further, the seed preparation step comprises the following: S01. Methyl methacrylate, glycidyl methacrylate and initiator are mixed, low-speed ultrasonic dispersion is performed, and a pre-dispersion liquid is obtained; S02. The emulsifier and polyethylene imine are mixed, dissolved with water, then the pre-dispersion liquid is added dropwise, ultrasonic emulsification is performed, and then heating reaction is performed, followed by demulsification, filtration, water washing, treatment in an immersion solution, filtration again, and drying to obtain an intermediate product A; S03. PE-g-MAH is taken, xylene is added, dissolved by heating, then nitrogen is passed, intermediate product A is added, catalytic reaction is performed, and then cooling and drying are performed to obtain the product. In the step S01, the mass ratio of methyl methacrylate, glycidyl methacrylate and initiator is (7-7.5):(3.2-3.5):(0.1-0.2); and the initiator is azobisisobutyronitrile.

[0010] Further, in the step S02, the heating reaction is performed at a temperature of 60-65℃ for 6-8h.

[0011] By adopting the technical scheme, the pre-dispersion liquid is used as an oil phase, and a micro-nano suspension emulsion is formed after ultrasonic emulsification in an aqueous phase; during the subsequent heating reaction process, monomer components and initiators are polymerized to obtain an elastomer polymer in the emulsion particles, and part of the polyethylene imine molecules participate in the initiation reaction at the water-oil interface to introduce a polar polyethylene imine chain segment on the surface of the elastomer; by virtue of the amine groups and other polar groups on the grafted polyethylene imine chain segment, divalent zinc ions and divalent copper metal ions can be effectively captured during the immersion process, so that the surface of the elastomer is assembled with metal active centers having antibacterial activity.

[0012] Furthermore, in step S02, the preparation of the impregnation solution includes the following steps: take zinc acetate and copper sulfate, add water to disperse them, add ammonia water dropwise, stir, and then add urea for further treatment to obtain the solution; the ratio of zinc acetate, copper sulfate, ammonia water and urea used is (0.5-0.8)g:(1.2-1.7)g:(1-2)mL:(0.2-0.3)g.

[0013] Furthermore, in step S03, the catalyst used in the catalytic reaction is triphenylphosphine, the temperature is set at 110-120℃, and the reaction lasts for 3-5 hours.

[0014] By employing the above technical solution, under the action of the catalyst triphenylphosphine, the residual epoxy groups on the elastomer polymer react with maleic anhydride, introducing nonpolar PE segments into the elastomer molecular chain. After crystallization and crushing treatment, the organic segments extending from the surface of the zeolite particles not only improve the compatibility between zeolite and the PE matrix, but also play an entanglement role similar to branched chain structures, enhancing the physical bond with the PE molecular chain, thereby inhibiting phase separation between the PE matrix and the modified zeolite.

[0015] This application also provides a modified moisture-absorbing composite membrane, which is prepared by the above-described preparation method.

[0016] Compared with the prior art, this application has the following beneficial effects: 1. This application describes the preparation of an organic elastomer via microemulsion polymerization, which is then used as a seed precursor for hydrothermal crystallization to obtain modified zeolite. This modified zeolite is then incorporated into a PE masterbatch and melt-extruded to produce a modified PE film with both excellent antibacterial and moisture-absorbing properties. The organic elastomer uses methyl methacrylate and glycidyl methacrylate as polymerizable monomers, which, in conjunction with polyethyleneimine, yield a highly chelating composition capable of forming stable chelate structures with antibacterial metal ions such as divalent zinc and divalent copper ions during impregnation. During subsequent hydrothermal crystallization of the zeolite, the seed crystal and the chelated metal ions are embedded into the zeolite framework, endowing the zeolite with long-lasting antibacterial activity and effectively inhibiting the dissolution of metal ions. Furthermore, the introduction of polar seed crystals enhances the polarity of the zeolite core, allowing water molecules to be physically adsorbed through the porous structure of the zeolite and attracted by the polar sites within the core, thereby significantly improving the overall moisture absorption capacity of the film.

[0017] 2. This application uses PE-g-MAH grafting treatment to introduce polyethylene segments on the surface of the seed crystal. The polyethylene segments partially exposed on the surface of the modified zeolite crystallization product can have good compatibility with the film base material PE in the melting stage, and play a physical entanglement role similar to that of the branched chain, so as to improve the compatibility between the modified zeolite and the PE base material. Attached Figure Description

[0018] Figure 1The results are the moisture absorption performance test results of the modified PE films in Examples 1-4 and Comparative Examples 1-3 of this application.

[0019] Figure 2 The results are the test results of the active metal ion desorption performance of the modified PE membranes in Examples 1-4 and Comparative Examples 1-3 of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0023] The terms "preferred," "more preferably," "better," and "even better" used in this application refer to embodiments of this application that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this application. That is, in this application, "preferred," "more preferably," "better," and "even better" are merely descriptions of implementations or embodiments with better effects, but do not constitute a limitation on the scope of protection of this application.

[0024] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0025] In this application, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0026] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method comprising steps (a) and (b) indicates that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0028] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0029] In this application, room temperature refers to 0~40℃, including but not limited to 10~40℃, or further to 20~30℃.

[0030] The present application will be further illustrated by the following examples, but these examples do not limit the scope of the present application.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this application, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are conventional products that can be purchased commercially. In addition to the specific methods, equipment, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description in this application, any prior art methods, equipment, and materials similar to or equivalent to those described, used, or made by the methods, equipment, and materials in the embodiments of this application may be used to implement this application.

[0032] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples and comparative examples are commercially available.

[0033] Description of raw materials used in the embodiments and comparative examples of this invention: Methyl methacrylate, CP, 98% (containing 30ppm MEHQ stabilizer), supplied by Shanghai E. En Chemical Technology Co., Ltd. Glycidyl methacrylate, AR, supplied by Guangdong Fangxin Biotechnology Co., Ltd. Emulsifier OP-10, supplied by Tianjin Zhonghe Shengtai Chemical Co., Ltd. Polyethyleneimine, AR, Mw=1800, supplied by Guangdong Yuanfeng Chemical Reagent Co., Ltd. PE-g-MAH, grade: TY1057H, supplied by Dongguan Zhangmutou Sike Plastic Raw Materials Business Department; Polyurethane adhesive, model: SY-176, solid content 71.3%, supplied by Huizhou Saiya Industrial Co., Ltd. Polyethylene masterbatch, grade: AMF705HF, supplied by Shulman Plastics, Inc., USA.

[0034] Preparation Example 1 Take 0.5g of zinc acetate and 1.2g of copper sulfate, add 50mL of deionized water to dissolve them, then add 1mL of ammonia water dropwise, adjust the magnetic stirring speed to 100rpm, process for 1min, and then add 0.2g of urea to prepare the impregnation solution.

[0035] Take 7g of methyl methacrylate, 3.2g of glycidyl methacrylate, 0.1g of azobisisobutyronitrile and 60mL of toluene and mix them at room temperature. Sonicate at 5kHz for 1min to obtain a pre-dispersion.

[0036] Take 120 mL of deionized water, 1.5 g of emulsifier OP-10 and 1.2 g of polyethyleneimine (Mw=1800), purge the system with nitrogen, adjust the magnetic stirring speed to 400 rpm and stir continuously. Then add 20 mL of pre-dispersion liquid dropwise at a rate of 3 mL / min, sonicate at 10 kHz for 5 min and then stop sonication. Adjust the magnetic stirring speed to 100 rpm and heat to 60 ℃ for 6 h. Then add 50 mL of saturated sodium chloride solution to the system and continue stirring for 10 min. After that, filter and take the solid part, wash it twice with water and put it in 50 mL of impregnation liquid. Adjust the magnetic stirring speed to 50 rpm and treat for 20 min. Then filter, take the filtrate and treat it with cold water for 1 min, and dry it to obtain intermediate product A.

[0037] 3.4 g of PE-g-MAH (MAH grafting rate of 0.5%) was mixed with 150 mL of xylene, and then heated to 110 °C. The magnetic stirring speed was adjusted to 300 rpm and continued for 1 h to obtain a homogeneous liquid. Nitrogen gas was then introduced, and 6.2 g of intermediate product A and 0.15 g of triphenylphosphine were added. After reacting for 3 h, heating was stopped, and the mixture was allowed to cool naturally to room temperature. After filtration and drying, seed crystals were obtained.

[0038] Preparation Example 2 Take 0.6g of zinc acetate and 1.5g of copper sulfate, add 50mL of deionized water to dissolve them, then add 1.2mL of ammonia water dropwise, adjust the magnetic stirring speed to 100rpm, treat for 3min, and then add 0.25g of urea to prepare the impregnation solution.

[0039] Take 7.2g of methyl methacrylate, 3.2g of glycidyl methacrylate, 0.15g of azobisisobutyronitrile and 65mL of toluene and mix them at room temperature. Sonicate at 5kHz for 1min to obtain a pre-dispersion.

[0040] Take 120 mL of deionized water, 1.5 g of emulsifier OP-10 and 1.5 g of polyethyleneimine (Mw=1800), purge the system with nitrogen, adjust the magnetic stirring speed to 400 rpm and stir continuously. Then add 20 mL of pre-dispersion liquid dropwise at a rate of 3.5 mL / min, sonicate at 10 kHz for 5 min and then stop sonication. Adjust the magnetic stirring speed to 200 rpm and heat to 65 ℃ for 7 h. Then add 50 mL of saturated sodium chloride solution to the system and continue stirring for 20 min. After that, filter and take the solid part, wash it with water 3 times and put it in 50 mL of impregnation liquid. Adjust the magnetic stirring speed to 150 rpm and treat for 30 min. Then filter, take the filtrate and treat it with cold water for 2 min, and dry it to obtain intermediate product A.

[0041] 3.9 g of PE-g-MAH (MAH grafting rate of 1%) was mixed with 150 mL of xylene, and then heated to 115 °C. The magnetic stirring speed was adjusted to 300 rpm and continued for 1.5 h to obtain a homogeneous liquid. Nitrogen gas was then introduced, and 6.8 g of intermediate product A and 0.15 g of triphenylphosphine were added. After reacting for 4.5 h, heating was stopped, and the mixture was allowed to cool naturally to room temperature. After filtration and drying, seed crystals were obtained.

[0042] Preparation Example 3 Take 0.8g of zinc acetate and 1.7g of copper sulfate, add 50mL of deionized water to dissolve them, then add 2mL of ammonia water dropwise, adjust the magnetic stirring speed to 100rpm, process for 1min, and then add 0.3g of urea to prepare the impregnation solution.

[0043] Take 7.5g methyl methacrylate, 3.5g glycidyl methacrylate, 0.2g azobisisobutyronitrile and 70mL toluene and mix at room temperature. Sonicate at 5kHz for 2min to obtain a pre-dispersion.

[0044] Take 120 mL of deionized water, 2 g of emulsifier OP-10 and 1.5 g of polyethyleneimine (Mw=1800), purge the system with nitrogen, adjust the magnetic stirring speed to 500 rpm and stir continuously. Then add 20 mL of pre-dispersion liquid dropwise at a rate of 5 mL / min, sonicate at 10 kHz for 10 min and then stop sonication. Adjust the magnetic stirring speed to 200 rpm and heat to 65 ℃ for 8 h. Then add 50 mL of saturated sodium chloride solution to the system and continue stirring for 20 min. After that, filter and take the solid part, wash it with water 3 times and put it in 50 mL of impregnation liquid. Adjust the magnetic stirring speed to 150 rpm and treat for 30 min. Then filter, take the filtrate and treat it with cold water for 2 min, and dry it to obtain intermediate product A.

[0045] 3.9 g of PE-g-MAH (MAH grafting rate of 1%) was mixed with 150 mL of xylene, and then heated to 120 °C. The magnetic stirring speed was adjusted to 300 rpm and continued for 2 h to obtain a homogeneous liquid. Nitrogen gas was then introduced, and 7.5 g of intermediate product A and 0.15 g of triphenylphosphine were added. After reacting for 5 h, heating was stopped, and the mixture was allowed to cool naturally to room temperature. After filtration and drying, seed crystals were obtained.

[0046] Example 1 The specific steps for preparing the modified moisture-absorbing composite membrane in this embodiment are as follows: Take PET film (thickness: 12 micrometers) and modified PE film (thickness: 50 micrometers), and mix them at 18.5 g / m³. 2 Polyurethane adhesive (model: SY-176) was applied to one side of the film, and then the adhesive side was laminated to the dark / light side of Al foil (thickness: 7 micrometers) respectively. The film was then naturally dried for 5 hours to obtain a modified moisture-absorbing composite film. The specific steps for preparing the modified PE film in this embodiment are as follows: Take 200g of calcined kaolin (1000 mesh, whiteness: 97%), 5g of seed crystals and 30g of sodium carbonate, mix them, grind them and pass them through a 1000 mesh sieve, dissolve them with 600mL of deionized water, then slowly add a 20% sodium silicate aqueous solution, adjust the silica-alumina ratio to 3.3, stir to obtain a mixed sol, then age it at room temperature for 10h and transfer it to a reaction vessel, hydrothermally crystallize it at 120℃ for 15h, then filter it, take the solid part, dry it and crush it, pass it through a 1000 mesh sieve to obtain modified zeolite.

[0047] Take 1.2 kg of polyethylene masterbatch and mix it with 50 g of modified zeolite for 1 min. Then place the mixture in a single-screw extrusion blow molding machine with a screw diameter of 20 mm, a length-to-diameter ratio of 25:1, and set the barrel temperature and die temperature to 150 °C and the blow ratio to 2:1 for extrusion blow molding to obtain a film thickness of 50 micrometers.

[0048] The seed crystal was prepared in Preparation Example 1.

[0049] Example 2 The specific steps for preparing the modified moisture-absorbing composite membrane in this embodiment are as follows: Take PET film (thickness: 12 microns) and modified PE film (thickness: 52 microns), and mix them at 18 g / m³. 2 Polyurethane adhesive (model: SY-176) was applied to one side of the film, and then the adhesive side was laminated with the dark / light side of Al foil (thickness: 7 micrometers) respectively. The film was then naturally dried for 6 hours to obtain a modified moisture-absorbing composite film. The specific steps for preparing the modified PE film in this embodiment are as follows: Take 250g of calcined kaolin (1000 mesh, whiteness: 97%), 8g of seed crystals and 35g of sodium carbonate, mix them, grind them and pass them through a 1000-mesh sieve, dissolve them with 600mL of deionized water, then slowly add a 25% sodium silicate aqueous solution, adjust the silica-alumina ratio to 3.3, stir to obtain a mixed sol, then age it at room temperature for 15h and transfer it to a reaction vessel, hydrothermally crystallize it at 145℃ for 16h, then filter it, take the solid part, dry it and crush it, pass it through a 1000-mesh sieve to obtain modified zeolite.

[0050] 1.35 kg of polyethylene masterbatch was mixed with 70 g of modified zeolite for 5 min. The mixture was then placed in a single-screw extrusion blow molding machine with a screw diameter of 20 mm, an aspect ratio of 25:1, a barrel temperature of 165 ℃, a die temperature of 155 ℃, and a blow-up ratio of 2.5:1 to produce a blown film with a film thickness of 52 micrometers.

[0051] The seed crystal was prepared in Preparation Example 2.

[0052] Example 3 The specific steps for preparing the modified moisture-absorbing composite membrane in this embodiment are as follows: Take PET film (thickness: 12 micrometers) and modified PE film (thickness: 55 micrometers), and mix them at 22 g / m³. 2 Polyurethane adhesive (model: SY-176) was applied to one side of the film, and then the adhesive side was laminated with the dark / light side of Al foil (thickness: 7 micrometers) respectively. The film was then naturally dried for 8 hours to obtain a modified moisture-absorbing composite film. The specific steps for preparing the modified PE film in this embodiment are as follows: Take 300g of calcined kaolin (1000 mesh, whiteness: 97%), 10g of seed crystals and 40g of sodium carbonate, mix them, grind them and pass them through a 1000 mesh sieve, dissolve them with 700mL of deionized water, then slowly add a 25% sodium silicate aqueous solution, adjust the silica-alumina ratio to 3.5, stir to obtain a mixed sol, then age at room temperature for 15h and transfer it to a reaction vessel, hydrothermally crystallize at 150℃ for 18h, then filter, take the solid part, dry it and crush it, pass it through a 1000 mesh sieve to obtain modified zeolite.

[0053] Take 1.5 kg of polyethylene masterbatch and mix it with 80 g of modified zeolite for 5 min. Then place the mixture in a single-screw extrusion blow molding machine with a screw diameter of 20 mm, an aspect ratio of 25:1, a barrel temperature of 165 ℃, a die temperature of 155 ℃, and a blow-up ratio of 2.5:1 to extrude and blow film, and obtain a film thickness of 55 micrometers.

[0054] The seed crystal was prepared in Preparation Example 3.

[0055] Example 4 The only difference between this embodiment and Embodiment 1 is that the mass of seed crystals used in the preparation of the modified zeolite is 5.5g.

[0056] The remaining steps are the same as in Example 1.

[0057] Comparative Example 1 The difference between this comparative example and Example 1 is that an equal amount of carboxymethyl cellulose was used instead of polyethyleneimine to prepare seed crystals.

[0058] The remaining steps are the same as in Example 1.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that an equal amount of ABS-g-MAH (MAH grafting rate of 1.2%) was used instead of PE-g-MAH to prepare seed crystals.

[0060] Among them, ABS-g-MAH is provided by Dongguan Nabaichuan Plastics Co., Ltd.

[0061] The remaining steps are the same as in Example 1.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that the preparation steps of the modified zeolite are as follows: Take 0.5g zinc acetate, 1.2g copper sulfate, and 1mL ammonia water, add 50mL deionized water to dissolve them, and then add 0.2g urea to prepare the impregnation solution.

[0063] Take 7g of methyl methacrylate, 3.2g of glycidyl methacrylate, 0.1g of azobisisobutyronitrile and 60mL of toluene and mix them at room temperature. Sonicate at 5kHz for 1min to obtain a pre-dispersion.

[0064] Take 120 mL of deionized water, 1.5 g of emulsifier OP-10 and 1.2 g of polyethyleneimine, purge the system with nitrogen, adjust the magnetic stirring speed to 400 rpm and stir continuously, then add 20 mL of pre-dispersion liquid dropwise at a rate of 3 mL / min, sonicate at 10 kHz for 5 min and then stop sonication, adjust the magnetic stirring speed to 100 rpm, heat to 60 ℃ and react for 6 h, then add 50 mL of saturated sodium chloride solution to the system and continue stirring for 10 min, then filter to collect the solid part, dry it to obtain intermediate product A.

[0065] 3.4 g of PE-g-MAH (MAH grafting rate of 0.5%) was mixed with 150 mL of xylene, and then heated to 110 °C. The magnetic stirring speed was adjusted to 300 rpm and continued for 1 h to obtain a homogeneous liquid. Nitrogen gas was then introduced, and 6.2 g of intermediate product A and 0.15 g of triphenylphosphine were added. After reacting for 3 h, heating was stopped, and the mixture was allowed to cool naturally to room temperature. After filtration and drying, seed crystals were obtained.

[0066] Take 250g of calcined kaolin (1000 mesh), 8g of seed crystals and 35g of sodium carbonate, mix them, grind them and pass them through a 1000 mesh sieve, dissolve them in 600mL of deionized water, then slowly add a 25% sodium silicate aqueous solution, adjust the silica-alumina ratio to 3.3, stir to obtain a mixed sol, then age at room temperature for 15h and transfer to a reactor, hydrothermally crystallize at 145℃ for 16h, then filter and take the solid part and place it in 50mL of impregnation solution, adjust the magnetic stirring speed to 50rpm and treat for 20min, then filter, take the filter collection and treat it with cold water for 1min, dry it and crush it through a 1000 mesh sieve to obtain modified zeolite.

[0067] The remaining steps are the same as in Example 1.

[0068] Performance testing 1. Apparent performance test The apparent properties of the modified moisture-absorbing composite membranes from Examples 1-4 and Comparative Examples 1-3 were tested, and the test items are shown in Table 1.

[0069] Table 1. Apparent performance test items of the modified moisture-absorbing composite films of Examples 1-4 and Comparative Examples 1-3 The test results are shown in Table 2.

[0070] Table 2. Apparent performance test results of the modified moisture-absorbing composite films of Examples 1-4 and Comparative Examples 1-3 Comparing Examples 1-4 and Comparative Examples 1-3 with Tables 1 and 2, it can be concluded that the absorbent membranes in the Examples 1-4 have intact surfaces without perforations or other defects. During the barrier performance test, the water vapor and oxygen permeability of the membranes remained at low levels. In contrast, Comparative Example 2, due to the addition of ABS-g-MAH treated modified zeolite to the membrane system, exhibited increased surface polarization of the zeolite and reduced compatibility with the PE base material. Perforations appeared in the melt-blown product after the modified zeolite was incorporated into the PE base material, resulting in a significant decrease in the barrier performance of the absorbent membrane in Comparative Example 2. Regarding the antibacterial properties of the membranes, the total aerobic bacteria count of the absorbent membranes in the Examples 1-4 was less than 1 cfu / 100 cm³. 2 The antibacterial properties are excellent. However, the antibacterial ability of the moisture-absorbing film prepared in Comparative Example 1 is slightly inferior to that of the Example scheme due to the limited ability of chelating divalent copper ions and divalent zinc ions to resist antibacterial metal ions during the seed preparation process. The microbial limits of Comparative Examples 2 and 3 are significantly increased compared to the Example scheme due to the influence of membrane integrity and effective antibacterial metal ion desorption, respectively. In all test groups, the modified moisture-absorbing PE film of the Example scheme can improve the storage time and effective life of the contents of the drug when applied to the pharmaceutical packaging film.

[0071] 2. Moisture absorption performance test Take the modified PE films from Examples 1-4 and Comparative Examples 1-3, cut them into 10mm × 10mm samples, and after thorough drying, place them in an environment with a relative humidity of 75±2% and a temperature of 30℃ for 24 hours. Record the sample mass m0 and m1 before and after the test, respectively. Then, remove the test samples and place them at room temperature and ventilation for 120 minutes, recording the sample mass m2 at this time. According to the formula: M = m1 - m0; R = (m1 - m2) / M × 100%; Where M: saturated moisture absorption capacity; R: residual moisture absorption rate.

[0072] Test results are as follows Figure 1 As shown.

[0073] Take Examples 1-4 and Comparative Examples 1-3 and combine them. Figure 1It can be concluded that the saturated moisture absorption capacity and residual moisture absorption rate of the modified moisture-absorbing membrane show a certain positive correlation trend in the test results. Judging from the saturated moisture absorption capacity data of Examples 1-4, within a certain range, the moisture absorption performance of the prepared modified PE membrane gradually improves with the increase of the amount of modified zeolite used in the PE base system. Due to the influence of the compatibility between the modified zeolite and the PE base system and the difference in the zeolite preparation process, the moisture absorption of the modified PE membrane prepared after melt mixing in Comparative Examples 2 and 3 is slightly reduced. In Comparative Example 1, carboxymethyl cellulose is used instead of polyethyleneimine. Due to the influence of molecular weight difference and the degree of interaction with the seed crystal, the polarity of the prepared modified zeolite is slightly lower than that of the example scheme, resulting in a decrease in the moisture absorption capacity of the modified zeolite.

[0074] 3. Desorption performance test of active metal ions Take the modified PE films from Examples 1-4 and Comparative Examples 1-3, and cut them into 10 test discs with a diameter of 1 cm using a punch. Then, take 5 discs from each group and immerse them in a 10% ethanol solution (volume denoted as V). Adjust the magnetic stirring speed to 50 rpm and soak for treatment (40℃, 24h). Afterward, collect the leachate and test it according to the national standard GB / T7475-1987 to detect the total ion concentration C of divalent copper ions and divalent zinc ions. Mix the remaining 5 test discs from each group and sinter them in a tube furnace at 550℃ for 30 min. Take the sintered ash from each group and soak it in 20 mL of 65% concentrated nitric acid and 2 mL of 10% hydrogen peroxide for 10 min. Then, calculate the total amount of divalent copper ions and divalent zinc ions N according to the national standard GB / T7475-1987. According to the formula: W = CV / N × 100%; The total desorption rate W of divalent copper ions and divalent zinc ions was calculated, and the results are as follows: Figure 2 As shown.

[0075] Take Examples 1-4 and Comparative Examples 1-3 and combine them. Figure 2 It can be concluded that the leaching rates of divalent copper and divalent zinc ions in the modified PE film of the example scheme are low, remaining below 1.51‰, while the schemes of Comparative Examples 1-3 all showed more serious leaching problems. Among them, the scheme of Comparative Example 3 uses the "crystallization before loading" treatment method to load antibacterial metal ions. In the desorption test, divalent copper and divalent zinc ions showed obvious desorption, which is detrimental to the packaging of pharmaceuticals. When the leached ions reach a certain dose, they may react with some active components in the pharmaceuticals, leading to a decrease in the activity of the pharmaceuticals. The carboxymethyl cellulose used in Comparative Example 1 has weaker chelating ability for divalent copper and divalent zinc metal ions than polyethyleneimine, which ultimately increases the amount of divalent copper and divalent zinc metal ions leached from the PE film.

[0076] Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a modified moisture-absorbing composite membrane, characterized in that, The preparation steps include the following: Following the stacking order from the outside to the inside, PET film, Al foil, and modified PE film are coated and laminated, followed by curing and drying to obtain a modified moisture-absorbing composite film. The preparation steps of the modified PE film include the following: The polyethylene masterbatch and modified zeolite are mixed and then extruded and blown into a film to obtain the final product. The preparation steps of the modified zeolite include the following: Calcined kaolin, seed crystals, and sodium carbonate are mixed and ground, dispersed with water, and the silicon-aluminum ratio is adjusted to 3.3-3.

5. The mixture is then aged, followed by a temperature-controlled crystallization process. After drying, the product is crushed and sieved to obtain the final product. The seed crystals are obtained by microemulsion polymerization of methyl methacrylate, glycidyl methacrylate and polyethyleneimine, followed by grafting the polymer product with PE-g-MAH.

2. The method for preparing a modified moisture-absorbing composite membrane according to claim 1, characterized in that, In the coating and lamination operation, the amount of adhesive applied is controlled at 20±2g / m². 2 .

3. The method for preparing a modified moisture-absorbing composite membrane according to claim 1, characterized in that, The mass ratio of polyethylene masterbatch to modified zeolite used is (120-150):(5-8); the extrusion blown film treatment is set with a barrel temperature of 150-165℃, a die temperature of 150-155℃, and a blow-up ratio of (2-2.5):1; the thickness of the modified PE film is 50-55 micrometers.

4. The method for preparing a modified moisture-absorbing composite membrane according to claim 1, characterized in that, In the preparation of the modified zeolite, the mass ratio of calcined kaolin, seed crystals, and sodium carbonate used is (40-60):(1-2):(6-8); The temperature-raising crystallization treatment is adjusted to 120-150℃ and treated for 15-18 hours.

5. The method for preparing a modified moisture-absorbing composite membrane according to claim 1, characterized in that, The preparation steps of the seed crystals include the following: S01. Take methyl methacrylate, glycidyl methacrylate and initiator, mix them, and disperse them by low-speed ultrasonication to obtain a pre-dispersion; S02. Mix emulsifier and polyethyleneimine, dissolve in water, then add pre-dispersion liquid dropwise, emulsify by ultrasound, heat and react, then demulsify, filter, wash with water, place in impregnation liquid for treatment, filter again, dry to obtain intermediate product A; S03. Take PE-g-MAH, add xylene, heat to dissolve, then purge with nitrogen, add intermediate product A, catalyze the reaction, then cool and dry to obtain seed crystals.

6. The method for preparing a modified moisture-absorbing composite membrane according to claim 5, characterized in that, In step S01, the mass ratio of methyl methacrylate, glycidyl methacrylate and initiator used is (7-7.5):(3.2-3.5):(0.1-0.2).

7. The method for preparing a modified moisture-absorbing composite membrane according to claim 5, characterized in that, In step S02, the temperature of the heating reaction is set at 60-65℃, and the reaction time is 6-8 hours.

8. The method for preparing a modified moisture-absorbing composite membrane according to claim 5, characterized in that, In step S02, the preparation steps of the impregnation solution include the following: take zinc acetate and copper sulfate, add water to disperse them, add ammonia water dropwise, stir, and then add urea for further treatment to obtain the solution; the ratio of zinc acetate, copper sulfate, ammonia water and urea used is (0.5-0.8)g:(1.2-1.7)g:(1-2)mL:(0.2-0.3)g.

9. The method for preparing a modified moisture-absorbing composite membrane according to claim 5, characterized in that, In step S03, the catalyst used in the catalytic reaction is triphenylphosphine, the temperature is set at 110-120℃, and the reaction lasts for 3-5 hours.

10. A modified moisture-absorbing composite membrane prepared by any one of the preparation methods described in claims 1-9.

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