Moisture absorption film with high barrier property and preparation method thereof

Abstract

The invention discloses a moisture absorption film with high barrier property and a preparation method thereof. The moisture absorption film comprises the following components in parts by mass: 180-200 parts of polyethylene resin, 30-40 parts of moisture absorption particles and 20-30 parts of high-barrier microspheres, the moisture absorption particles are beeswax coated calcium oxide particles; the high-barrier microspheres are porous polymer microspheres loaded with 3, 4, 5-trihydroxybenzoic acid, and the porous polymer microspheres adopt an ethylene-vinyl alcohol copolymer. The moisture absorption particles and the high-barrier microspheres with special components are added into the PE film, so that the moisture absorption capacity and the barrier property of the PE film can be remarkably improved, and meanwhile, the film layer is prevented from being released into a packaging cavity after absorbing moisture.

Description

Technical Field

[0001] The present invention relates to the technical field of pharmaceutical packaging materials, in particular to a hygroscopic film with high barrier properties and a preparation method thereof. Background Art

[0002] Humidity is a common environmental indicator in everyday life, and the relative humidity within buildings significantly impacts human health and living comfort. Surveys have found that when indoor relative humidity is below 40% or above 65%, bacteria and viruses multiply significantly, potentially causing or exacerbating respiratory illnesses. As living standards continue to improve, people are increasingly paying attention to humidity regulation.

[0003] To prevent food or medicine from spoiling due to exposure to air and moisture, a conventional practice is to place a desiccant inside the package. However, since the desiccant comes into contact with the food or medicine, there is a safety risk of a reaction with the desiccant. Furthermore, desiccants use microporous technology to absorb moisture. The desiccant itself contains fine particles, which may contaminate the contents to a certain extent. Furthermore, after absorbing moisture, conventional desiccants tend to re-emit the moisture. Therefore, the moisture absorption effect is reversible, which is not conducive to the long-term storage of packaged medicines and food.

[0004] Therefore, developing packaging films with hygroscopic properties is a key approach to achieving air and moisture barrier properties. Hygroscopic packaging prevents food and pharmaceutical spoilage by blocking external moisture from entering the package and removing moisture from within. PE film offers excellent mechanical properties and chemical stability. Composed of hydrocarbons, PE is inherently low in toxicity, making it one of the most hygienic plastics. Therefore, it is commonly used in industrial packaging for food, pharmaceuticals, medical devices, and other products. However, existing PE films have poor hygroscopic properties, and external moisture can be released back into the package after being coated. Furthermore, PE has a high oxygen permeability, making it difficult to meet the requirements for hygroscopic barrier properties.

[0005] In view of this, this application is hereby filed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the existing PE film has poor moisture absorption effect. The external moisture may be released again into the package after being coated with the film layer. In addition, the oxygen permeability of PE is also high, so it is difficult to meet the moisture absorption barrier requirements. The purpose is to provide a moisture-absorbing film with high barrier properties and a preparation method thereof. By adding moisture-absorbing particles and high-barrier microspheres of special components to the PE film, the moisture absorption capacity and barrier performance of the PE film can be significantly improved, while preventing the film layer from absorbing moisture and then releasing it into the packaging cavity.

[0007] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a hygroscopic film with high barrier properties, comprising the following components in parts by weight: 180-200 parts of polyethylene resin, 30-40 parts of hygroscopic microparticles, and 20-30 parts of high barrier microspheres; The hygroscopic particles are beeswax-coated calcium oxide particles; The high-barrier microspheres are porous polymer microspheres loaded with 3,4,5-trihydroxybenzoic acid.

[0008] The present invention significantly improves the moisture absorption capacity and barrier performance of the PE film by adding hygroscopic particles and high-barrier microspheres of special components to the PE film, while preventing the film layer from absorbing moisture and then releasing it into the packaging cavity.

[0009] The hygroscopic particles used in the present invention are beeswax-coated calcium oxide particles. At room temperature, low temperature and low humidity, the beeswax coats the calcium oxide particles in a solid state. The beeswax itself has good hygroscopicity. Therefore, when the humidity is low, the beeswax can absorb moisture. At the same time, due to the difference in the internal and external structures of the hygroscopic particles, the absorbed moisture can penetrate into the interior of the hygroscopic particles and react with the calcium oxide to achieve "irreversible" reaction, thereby locking the moisture. The fixed beeswax coating further ensures that the moisture is locked inside the hygroscopic particles. If the humidity or temperature in the environment continues to increase, the outer layer of beeswax will continue to soften and deform, exposing the calcium oxide particles inside the hygroscopic particles, increasing the area of ​​direct contact between the moisture that penetrates the film and the calcium oxide, thereby directly adsorbing moisture through the exposed calcium oxide particles to react and generate calcium hydroxide, significantly improving the hygroscopic capacity of the PE film and preventing moisture outside the film layer from passing through the film layer into the interior of the package.

[0010] In one specific embodiment, the beeswax layer coating the hygroscopic particles is porous and comprises 90-95% beeswax and 5-10% gelatin. The porous structure of the beeswax layer allows for partial exposure of the calcium oxide surface. Furthermore, it results in a non-uniform thickness across the entire coating interface. When the beeswax softens and deforms in high-humidity and high-temperature environments, thinner areas of the layer quickly "break" and deform toward thicker areas, rapidly forming pores that penetrate the calcium oxide, exposing more of the calcium oxide surface. Thicker areas of the layer experience relatively little deformation. When the ambient humidity and temperature decrease, the layer solidifies again, encapsulating a portion of the calcium oxide surface and thus "locking" the adsorbed moisture. Furthermore, the porous structure of the beeswax layer allows the calcium hydroxide precipitate, formed when the calcium oxide reacts with water, to be located within the porous structure, thereby preventing deformation of the film layer caused by molecular volume expansion and affecting its mechanical properties. Furthermore, solid beeswax exhibits excellent slip toughness, so the presence of the beeswax layer can also enhance toughness to a certain extent, improving mechanical properties. The present invention further adds a small amount of gelatin to the beeswax layer, which also has good water absorption capacity. At the same time, the gelatin has a three-dimensional network structure inside. When the beeswax softens, it can play a certain pulling and supporting role on the layered structure of the beeswax.

[0011] In a specific embodiment, the preparation method of the hygroscopic particles is as follows: Heat beeswax to 60-70°C until it is melted, add gelatin and continue stirring, finally add pore-forming agents polyoxyethylene ether and calcium oxide in sequence and stir evenly, then cool to room temperature, crush and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic particles.

[0012] In a specific embodiment, the mass ratio of beeswax to calcium oxide is 1:2~3.

[0013] The high-barrier microspheres used in the present invention are porous polymer microspheres loaded with 3,4,5-trihydroxybenzoic acid. These porous polymer microspheres are made of ethylene-vinyl alcohol copolymer, which has a tightly structured polymer chain. Its alternating arrangement of ethylene and vinyl alcohol monomer units provides excellent gas barrier properties. When prepared as microspheres and doped in a PE film, these microspheres can prevent external oxygen from penetrating and passing through the film. Furthermore, ethylene-vinyl alcohol copolymer also exhibits excellent mechanical strength, elasticity, and wear resistance. Therefore, its addition as a reinforcing particle to a PE film can also improve the film's mechanical properties.

[0014] 3,4,5-trihydroxybenzoic acid can react with oxygen to absorb it, and loading it in porous polymer microspheres can synergistically improve the barrier effect on oxygen; since there are hydroxyl groups in the molecular structure of ethylene-vinyl alcohol copolymer, it is also hydrophilic and hygroscopic, and can absorb moisture and improve the hygroscopic performance of PE film; however, after absorbing moisture, the barrier performance of ethylene-vinyl alcohol copolymer to oxygen will be affected. Therefore, the present invention loads 3,4,5-trihydroxybenzoic acid on porous ethylene-vinyl alcohol copolymer microspheres. First, the carboxyl group of 3,4,5-trihydroxybenzoic acid can bond with a part of the hydroxyl groups of ethylene-vinyl alcohol copolymer, reducing the absorption of water by ethylene-vinyl alcohol copolymer. Secondly, 3,4,5-trihydroxybenzoic acid has more hydroxyl groups, which, on the one hand, further improves the moisture absorption effect; on the other hand, the hydroxyl groups of 3,4,5-trihydroxybenzoic acid can compete with the hydroxyl groups in the ethylene-vinyl alcohol copolymer for water molecules, reducing the impact on the barrier properties of the ethylene-vinyl alcohol copolymer after moisture absorption. Finally, high concentrations of water vapor can further activate the oxygen absorption reaction of 3,4,5-trihydroxybenzoic acid and accelerate the absorption of oxygen by 3,4,5-trihydroxybenzoic acid; therefore, the porous polymer microspheres loaded with high-barrier microspheres of 3,4,5-trihydroxybenzoic acid, the two synergistically not only further enhance the moisture absorption effect of the PE film, but also improve the oxygen barrier ability of the film layer.

[0015] In a specific embodiment, the mass ratio of the porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 4-5:1.

[0016] In a specific embodiment, the preparation method of the high barrier microspheres is as follows: dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution is slowly added dropwise to the polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system is subjected to high-speed oscillation emulsification, and the solvent is removed, washed, and dried to obtain porous polymer microspheres; 3,4,5-trihydroxybenzoic acid is added to anhydrous ethanol and stirred to dissolve, and then porous polymer microspheres are added and stirred continuously to form a dispersion, and the solvent is separated and dried to obtain the high-barrier microspheres.

[0017] In a second aspect, the present invention provides a method for preparing a hygroscopic film with high barrier properties, characterized in that it comprises the following steps: 1) Heat beeswax to melt, add gelatin and continue stirring, finally add pore-forming agent and calcium oxide in sequence and stir evenly, cool to room temperature, crush and remove the pore-forming agent to obtain hygroscopic particles; 2) adding 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stirring to dissolve, then adding porous polymer microspheres and continuously stirring to form a dispersion, separating the solvent, and drying to obtain the high-barrier microspheres; 3) Hygroscopic microparticles, high barrier microspheres and polyethylene resin are added to a screw machine for mixing and granulation to obtain PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The embodiments of the present invention provide a hygroscopic film with high barrier properties and a preparation method. By adding hygroscopic particles and high-barrier microspheres of a special component to the PE film, the PE film's moisture absorption capacity and barrier properties can be significantly improved, while preventing the film from absorbing moisture and then releasing it into the packaging cavity. 2. The embodiments of the present invention provide a hygroscopic film with high barrier properties and a preparation method thereof. The hygroscopic particles are beeswax-coated calcium oxide particles. At room temperature, low temperature, and low humidity, the beeswax coats the calcium oxide particles in a solid state. Beeswax itself has good hygroscopicity. Therefore, at low humidity, the beeswax can absorb moisture. At the same time, due to the difference in the internal and external structures of the hygroscopic particles, the absorbed moisture can penetrate into the interior of the hygroscopic particles and react with the calcium oxide to achieve "irreversible" moisture locking. The fixed beeswax coating further ensures that the moisture is locked inside the hygroscopic particles. 3. The embodiments of the present invention provide a hygroscopic film with high barrier properties and a preparation method. As humidity or temperature increases, the beeswax on the outer layer of the hygroscopic particles gradually softens and deforms, exposing the calcium oxide particles within the hygroscopic particles. This increases the area of ​​direct contact between water that penetrates the film and the calcium oxide. As a result, the exposed calcium oxide particles directly absorb water to react and form calcium hydroxide, significantly improving the hygroscopic capacity of the PE film and preventing moisture from passing through the film layer into the packaging. 4. The embodiments of the present invention provide a hygroscopic film with high barrier properties and a preparation method. The high-barrier microspheres are porous polymer microspheres loaded with 3,4,5-trihydroxybenzoic acid. The ethylene-vinyl alcohol copolymer has a tightly structured polymer chain. Its alternating arrangement of ethylene and vinyl alcohol monomer units can provide an excellent barrier effect against gases. The microspheres prepared by doping the ethylene-vinyl alcohol copolymer into a PE film can prevent external oxygen from penetrating and passing through the film layer. At the same time, the ethylene-vinyl alcohol copolymer also has good mechanical strength, elasticity, and wear resistance. Therefore, adding the ethylene-vinyl alcohol copolymer as a reinforcing particle into the PE film can also improve the mechanical properties of the PE film. 5. The embodiments of the present invention provide a hygroscopic film with high barrier properties and a preparation method. 3,4,5-trihydroxybenzoic acid can react with oxygen to absorb it, and loading it into porous polymer microspheres can synergistically improve the barrier effect against oxygen. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0020] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other embodiments, well-known methods are not specifically described to avoid obscuring the present invention.

[0021] Throughout this specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Therefore, appearances of the phrases "one embodiment," "an embodiment," "an example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable combinations and / or subcombinations in one or more embodiments or examples.

[0022] Example 1 An embodiment of the present invention provides a method for preparing a hygroscopic film with high barrier properties, comprising the following steps: 1) Heat beeswax to 60-70°C until it is molten, add pore-forming agent polyoxyethylene ether and calcium oxide in sequence and stir evenly. The mass ratio of beeswax, calcium oxide, and polyoxyethylene ether is 1:2:0.01. Cool to room temperature, crush, and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic particles. 2) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt % polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres (this step adopts a conventional porous microsphere preparation method and is not described in detail); Add 3,4,5-trihydroxybenzoic acid to anhydrous ethanol, stir to dissolve, then add porous polymer microspheres and continue stirring to form a dispersion, wherein the mass ratio of porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 4:1, separate the solvent, and dry to obtain the high-barrier microspheres; 3) Hygroscopic microparticles, high-barrier microspheres, and polyethylene resin are added to a screw machine for mixing and granulation to obtain a PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 180 parts, the hygroscopic microparticles 30 parts, and the high-barrier microspheres 20 parts.

[0023] Example 2 An embodiment of the present invention provides a method for preparing a hygroscopic film with high barrier properties, comprising the following steps: 1) Heat beeswax to 60-70°C until molten, add pore-forming agent polyoxyethylene ether and calcium oxide in sequence and stir evenly. The mass ratio of beeswax, calcium oxide, and polyoxyethylene ether is 1:2.5:0.01. Cool to room temperature, crush, and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic microparticles. 2) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt% polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres; Add 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stir to dissolve, then add porous polymer microspheres and continue stirring to form a dispersion, wherein the mass ratio of porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 4.5:1, separate the solvent, and dry to obtain the high-barrier microspheres; 3) Hygroscopic microparticles, high-barrier microspheres, and polyethylene resin are added to a screw machine for mixing and granulation to obtain a PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 190 parts, the hygroscopic microparticles 35 parts, and the high-barrier microspheres 25 parts.

[0024] Example 3 An embodiment of the present invention provides a method for preparing a hygroscopic film with high barrier properties, comprising the following steps: 1) Heat beeswax to 60-70°C until molten, then add pore-forming agents polyoxyethylene ether and calcium oxide in sequence and stir evenly. The mass ratio of beeswax, calcium oxide, and polyoxyethylene ether is 1:3:0.01, and the ratio of beeswax to gelatin is 9:1. Cool to room temperature, crush, and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic microparticles. 2) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt% polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres; Add 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stir to dissolve, then add porous polymer microspheres and continue stirring to form a dispersion, wherein the mass ratio of porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 5:1, separate the solvent, and dry to obtain the high-barrier microspheres; 3) Hygroscopic microparticles, high-barrier microspheres, and polyethylene resin are added to a screw machine for mixing and granulation to obtain a PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 200 parts, the hygroscopic microparticles 40 parts, and the high-barrier microspheres 30 parts.

[0025] Comparative Example 1 This comparative example provides a method for preparing a hygroscopic film, comprising the following steps: 1) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt % polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres (this step adopts a conventional porous microsphere preparation method and is not described in detail); Add 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stir to dissolve, then add porous polymer microspheres and continue stirring to form a dispersion, wherein the mass ratio of porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 5:1, separate the solvent, and dry to obtain the high-barrier microspheres; 2) High-barrier microspheres and polyethylene resin are added to a screw machine for mixing and granulation to obtain PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 200 parts and the high-barrier microspheres comprises 30 parts.

[0026] The difference between this comparative example and Example 3 is that the hygroscopic film does not contain hygroscopic particles.

[0027] Comparative Example 2 This comparative example provides a method for preparing a hygroscopic film, comprising the following steps: 1) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt% polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres; Add 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stir to dissolve, then add porous polymer microspheres and continue stirring to form a dispersion, wherein the mass ratio of porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 5:1, separate the solvent, and dry to obtain the high-barrier microspheres; 2) Calcium oxide, high-barrier microspheres, and polyethylene resin are added to a screw machine for mixing and granulation to obtain a PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 200 parts, calcium oxide 40 parts, and high-barrier microspheres 30 parts.

[0028] The difference between this comparative example and Example 3 is that the calcium oxide is not coated with a porous beeswax layer.

[0029] Comparative Example 3 This comparative example provides a method for preparing a hygroscopic film, comprising the following steps: 1) Heat beeswax to 60-70°C until molten, then add pore-forming agents polyoxyethylene ether and calcium oxide in sequence and stir evenly. The mass ratio of beeswax, calcium oxide, and polyoxyethylene ether is 1:3:0.01, and the ratio of beeswax to gelatin is 9:1. Cool to room temperature, crush, and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic microparticles. 2) Hygroscopic microparticles and polyethylene resin are added to a screw machine for mixing and granulation to obtain PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 200 parts and the hygroscopic microparticles comprises 40 parts.

[0030] The difference between this comparative example and Example 3 is that the hygroscopic film does not contain high-barrier microspheres.

[0031] Comparative Example 4 The present comparative example provides a method for preparing a hygroscopic film, comprising the following steps: 1) Heat beeswax to 60-70°C until molten, then add pore-forming agents polyoxyethylene ether and calcium oxide in sequence and stir evenly. The mass ratio of beeswax, calcium oxide, and polyoxyethylene ether is 1:3:0.01, and the ratio of beeswax to gelatin is 9:1. Cool to room temperature, crush, and remove the pore-forming agent with anhydrous ethanol to obtain hygroscopic microparticles. 2) dissolving ethylene-vinyl alcohol copolymer in chloroform to obtain a copolymer solution; The copolymer solution was slowly added dropwise to a 2 wt% polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system was subjected to high-speed oscillation emulsification, and the solvent was removed, washed, and dried to obtain porous polymer microspheres; 3) Hygroscopic microparticles, porous polymer microspheres and polyethylene resin are added to a screw machine for mixing and granulation to obtain PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties; wherein the polyethylene resin comprises 200 parts, the hygroscopic microparticles 40 parts and the porous polymer microspheres 30 parts.

[0032] The difference between this comparative example and Example 3 is that the high-barrier microspheres are not loaded with 3,4,5-trihydroxybenzoic acid.

[0033] Comparative Example 5 This comparative example provides a hygroscopic film. The difference between this comparative example and Example 3 is that the calcium oxide is not coated with a porous beeswax layer, and the high-barrier microspheres are not loaded with 3,4,5-trihydroxybenzoic acid.

[0034] Comparative Example 6 This comparative example provides a hygroscopic film. The difference between this comparative example and Example 3 is that this comparative example does not include hygroscopic particles and high-barrier microspheres, and only contains polyethylene resin.

[0035] The PE hygroscopic films prepared in Examples 1-3 and Comparative Examples 1-6 were tested for mechanical properties, moisture absorption, and barrier properties. The test conditions were normal temperature (25°C, 50% humidity) and high temperature and high humidity (40°C, 75% humidity). The results are shown in Table 1.

[0036] Table 1

[0037] Table 2

[0038] Table 3

[0039] It can be seen from Tables 1 to 3 above that the PE hygroscopic films prepared in Examples 1 to 3 of the present invention have good hygroscopic and barrier properties, and the mechanical properties of the film layers are significantly improved.

[0040] As can be seen from Comparative Example 1, the film was not added with hygroscopic particles, so its hygroscopic performance was significantly reduced, and its barrier performance and mechanical properties were also reduced. As can be seen from Comparative Example 2, the hygroscopic particles added to the film were not coated with beeswax, and its hygroscopic performance and barrier performance were only slightly reduced, while the mechanical properties were significantly reduced. This is because the calcium oxide particles absorbed water and the system expanded, thus affecting the mechanical properties of the film layer. As can be seen from Comparative Example 3, the film was not added with high-barrier microspheres, and its hygroscopic performance was only slightly reduced. However, its barrier properties and mechanical properties are significantly reduced; as can be seen from Comparative Example 3, the addition of high-barrier microspheres to the film, but the microspheres are not loaded with 3,4,5-trihydroxybenzoic acid, has no significant effect on its hygroscopic properties and mechanical properties, but the oxygen permeability is significantly increased, indicating that the film layer's barrier to oxygen is significantly reduced; as can be seen from Comparative Example 5, the simultaneous addition of hygroscopic particles not coated with beeswax and high-barrier microspheres not loaded with 3,4,5-trihydroxybenzoic acid reduces its hygroscopic properties, while significantly reduces its barrier properties and mechanical properties. The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hygroscopic film with high barrier properties, characterized in that The invention comprises the following components in parts by weight: 180-200 parts of polyethylene resin, 30-40 parts of hygroscopic microparticles, and 20-30 parts of high barrier microspheres; The hygroscopic particles are calcium oxide particles coated with a beeswax layer; The high-barrier microspheres are porous polymer microspheres loaded with 3,4,5-trihydroxybenzoic acid.

2. A hygroscopic film with high barrier properties according to claim 1, characterized in that: The beeswax layer coated on the outside of the hygroscopic particles has a porous structure, and the beeswax layer comprises 90-95% beeswax and 5-10% gelatin.

3. The hygroscopic film with high barrier properties according to claim 2, characterized in that: The mass ratio of the beeswax to calcium oxide is 1:2-3.

4. The hygroscopic film with high barrier properties according to claim 2, characterized in that: The preparation method of the hygroscopic particles is as follows: The beeswax is heated and melted to a molten state, gelatin is added and continued to be stirred, and finally a pore-forming agent and calcium oxide are added in sequence and stirred evenly, and then cooled to room temperature, crushed and the pore-forming agent is removed to obtain hygroscopic microparticles.

5. The hygroscopic film with high barrier properties according to claim 4, characterized in that: The pore-forming agent is polyoxyethylene ether, and the pore-forming agent is removed by using anhydrous ethanol.

6. The hygroscopic film with high barrier properties according to claim 1, characterized in that: The porous polymer microspheres are made of ethylene-vinyl alcohol copolymer.

7. The hygroscopic film with high barrier properties according to claim 6, characterized in that: The mass ratio of the porous polymer microspheres to 3,4,5-trihydroxybenzoic acid is 4-5:

1.

8. The hygroscopic film with high barrier properties according to claim 6, characterized in that: The preparation method of the high barrier microspheres is as follows: dissolving ethylene-vinyl alcohol copolymer in an oil phase organic solvent to obtain a copolymer solution; The copolymer solution is slowly added dropwise to the polyvinyl alcohol aqueous solution to form a mixed solution system, and the mixed solution system is subjected to high-speed oscillation emulsification, and the solvent is removed, washed, and dried to obtain porous polymer microspheres; 3,4,5-trihydroxybenzoic acid is added to anhydrous ethanol and stirred to dissolve, and then porous polymer microspheres are added and stirred continuously to form a dispersion, and the solvent is separated and dried to obtain the high-barrier microspheres.

9. The hygroscopic film with high barrier properties according to claim 8, characterized in that: The oil phase organic solvent is chloroform.

10. The method for preparing a hygroscopic film with high barrier properties according to any one of claims 1 to 9, characterized in that: The steps include: 1) Heat beeswax to melt, add gelatin and continue stirring, finally add pore-forming agent and calcium oxide in sequence and stir evenly, cool to room temperature, crush and remove the pore-forming agent to obtain hygroscopic particles; 2) adding 3,4,5-trihydroxybenzoic acid to anhydrous ethanol and stirring to dissolve, then adding porous polymer microspheres and continuously stirring to form a dispersion, separating the solvent, and drying to obtain the high-barrier microspheres; 3) Hygroscopic microparticles, high barrier microspheres and polyethylene resin are added to a screw machine for mixing and granulation to obtain PE film masterbatch, which is then fed into an extruder to produce a PE hygroscopic film with high barrier properties.

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