Packaging film, preparation method and packaging bag

Abstract

The invention discloses a packaging film, a preparation method and a packaging bag, and belongs to the technical field of packaging materials, the packaging film at least comprises a high-molecular polymer film, a bonding layer and an aluminum foil; the bonding layer is positioned between the high-molecular polymer film and the aluminum foil; the raw material of the bonding layer comprises 8-12wt% of functional core-shell acrylate particles; the functional core-shell acrylate particles comprise carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles in a mass ratio of (1-2): 1. The bonding layer added with functional core-shell acrylate particles can effectively resist cracks and stress concentration generated under dynamic rubbing, the structural stability of the packaging film is maintained, a dynamic cross-linked network is formed between carboxyl and epoxy groups, stress can be effectively dispersed, and the service life of the packaging film is prolonged. The interface bonding force between the bonding layer and the high-molecular polymer film as well as the aluminum foil can be enhanced, and the finally obtained packaging film has good rubbing resistance and also has good barrier property after rubbing.

Description

Technical Field

[0001] This invention belongs to the field of packaging materials technology, specifically relating to a packaging film, a preparation method, and a packaging bag. Background Technology

[0002] Due to the protein, fat, and other components in food, as well as their susceptibility to microbial growth, food packaging materials must possess a certain degree of barrier properties. Good oxygen barrier properties can reduce the amount of oxygen from the environment penetrating into the packaging, preventing food from spoiling due to mold, oxidation, or other deterioration issues. Good barrier properties are of great significance for extending the shelf life of food.

[0003] Aluminum foil possesses numerous excellent properties, including lightweight, high barrier properties, light-blocking, UV resistance, moisture resistance, corrosion resistance, and rapid heat conduction. Furthermore, aluminum foil is highly adaptable to processing and can be directly laminated with plastic film to create aluminum-plastic composite packaging with high barrier properties. This packaging can be used for cooked meat products, space foods, sauces, or pastes, extending the shelf life of these foods.

[0004] However, during the production of aluminum foil, due to limitations in raw materials, processes, and workshop environment, unavoidable micro-pinholes inevitably form on the surface, affecting its barrier properties to some extent. Aluminum-plastic composite packaging materials, made from aluminum foil and plastic film, are inevitably subjected to folding, bending, and other abrasive forces during food sterilization, vacuuming, or finished product transportation and storage. This causes the pinholes on the aluminum foil surface to gradually enlarge, damaging the layer structure of the packaging material and significantly reducing its barrier properties. In some cases, penetrating pinholes may even lead to leakage, ultimately affecting the shelf life of the packaging material. Summary of the Invention

[0005] The purpose of this invention is to provide a packaging film, a preparation method, and a packaging bag to solve the problem of poor tear resistance of aluminum-plastic composite packaging materials.

[0006] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a packaging film comprising at least a polymer film, an adhesive layer, and an aluminum foil; the adhesive layer is located between the polymer film and the aluminum foil; The adhesive layer consists of 8-12 wt% functional core-shell acrylate particles; the functional core-shell acrylate particles include carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles in a mass ratio of (1-2):1.

[0007] Preferably, the adhesive layer also includes a polyurethane adhesive; the polyurethane adhesive includes one or a combination of two of polyether polyurethane and polyester polyurethane.

[0008] Preferably, the polymer membrane includes any one of polyethylene terephthalate membrane, polypropylene membrane, polyethylene membrane, and polyamide membrane.

[0009] By adopting the above technical solution, the present invention also adds core-shell acrylate particles to the adhesive layer. This is because traditional adhesives, including the polyurethane adhesives selected in this invention, are prone to brittle fracture under dynamic rubbing stress, leading to interface peeling or new stress concentration between the adhesive and the aluminum foil, which reduces the rubbing resistance of the packaging film and thus reduces the performance of the packaging film.

[0010] The core-shell acrylate particles consist of a soft core layer and a hard shell layer. When dispersed in the adhesive layer, the soft core layer enhances the elastic modulus and elongation at break of the adhesive layer, ensuring that the composite packaging film maintains its adhesive integrity under dynamic rubbing and improving the overall structural stability of the packaging film. The hard shell layer effectively stops the propagation of crazing and, in conjunction with the soft core layer, absorbs impact energy, forming multiple energy dissipation paths to prevent stress damage to the adhesive layer and inhibit brittle fracture under rubbing stress.

[0011] The packaging film, which connects aluminum foil and polymer film with an adhesive layer containing core-shell acrylate particles, can prevent micro-cracks caused by rubbing, inhibit the spread of cracks to adjacent layers, maintain the barrier properties of the packaging film, and also help the adhesive layer form a uniform stress field when under stress, reducing aluminum foil breakage or delamination caused by local stress concentration.

[0012] Furthermore, the core-shell acrylate particles of the present invention are a blend of carboxylated core-shell acrylate particles and epoxy acrylate particles. Different functional groups are introduced on the core-shell acrylate particles. The carboxyl groups and epoxy groups can react and connect with each other. On the one hand, this can enhance the chemical bonding force between the core-shell particles and the adhesive layer substrate. On the other hand, the dynamic cross-linking network formed between the carboxyl groups and epoxy groups can further effectively disperse the shear stress generated by dynamic kneading and reduce the risk of stress concentration.

[0013] The addition of two types of functionalized core-shell particles can also strengthen the interfacial bonding between the adhesive layer and the polymer film and aluminum foil. Insufficient affinity between ordinary adhesives and aluminum foil, uneven coating or excessive surface tension will lead to poor leveling, forming spots or white spots, reducing the barrier performance of the packaging film, and causing the layers to separate after being rubbed, resulting in poor structural stability.

[0014] The addition of carboxyl and epoxy groups can form hydrogen bonds or chemical bonds with the polar groups on the aluminum foil surface, thereby significantly improving the interfacial bonding strength between the adhesive layer and the aluminum foil. After heat curing, the epoxy groups can also form hydrogen bonds or covalent bonds with the amino groups in the adhesive and the polymer film, further improving the peel strength of the packaging film and enhancing its structural stability and barrier properties.

[0015] Preferably, the raw materials for the carboxylated core-shell acrylate particles include butyl acrylate, methyl methacrylate, and carboxyacrylate monomers in a mass ratio of 100:(20-30):(5-10); the raw materials for the epoxidized core-shell acrylate particles include butyl acrylate, methyl methacrylate, and epoxy acrylate monomers in a mass ratio of 100:(20-30):(5-10).

[0016] Preferably, the carboxyacrylate monomer includes one or more of methacrylic acid, methacryloyloxyethyl succinate and methacryloyloxyethyl maleic acid monoester; the epoxyacrylate monomer includes one or more of glycidyl methacrylate, glycidyl acrylate and phenyl glycidyl ether acrylate.

[0017] Preferably, the functional core-shell acrylate particles are prepared according to the following method: S101. Add emulsifier to water, mix well, keep the solution temperature at 70-80℃, add 5-8wt% butyl acrylate and crosslinking agent, stir for 10-20min, add initiator, stir reaction for 60-90min to obtain seed emulsion; S102. Add the remaining butyl acrylate to the seed emulsion, along with the emulsifier and crosslinking agent. After 40-60 minutes, add the initiator to induce core layer growth and obtain a core layer emulsion. S103. Add carboxylated acrylic monomer or epoxy acrylic monomer, emulsifier and methyl methacrylate to the core emulsion. After 30-40 min, add an initiator to initiate shell growth. Keep the solution temperature at 75-85℃. After 1-2 h, cool, filter, freeze, wash, filter and dry to obtain carboxylated core-shell acrylate particles or epoxidized core-shell acrylate particles. S104. Functional core-shell acrylate particles are obtained by mixing carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles.

[0018] Preferably, the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate; the crosslinking agent includes one or more of allyl methacrylate, 1,4-butanediol diacrylate, ethylene glycol diacrylate, and trimethylolpropane triacrylate; and the initiator includes one or more of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

[0019] By employing the above-mentioned technical methods, this invention uses butyl acrylate as the core material and methyl methacrylate as the shell material. Core-shell acrylate particles are obtained through an emulsification reaction. During the formation of the shell, carboxylated acrylic monomers or epoxy-based acrylic monomers are added as functionalizing agents to introduce carboxyl or epoxy groups onto the surface of the core-shell acrylate particles. Then, the obtained carboxylated core-shell acrylate particles are mixed with epoxidized core-shell acrylate particles in a corresponding mass ratio to obtain functional core-shell acrylate particles.

[0020] The resulting functional core-shell acrylate particles not only enhance the bonding force with the adhesive layer substrate, preventing excessive agglomeration and effectively increasing the toughness of the adhesive layer, but also inhibit brittle fracture under dynamic rubbing stress, improving the rubbing resistance and barrier properties of the packaging film and enhancing structural stability. Furthermore, they improve the interfacial bonding force between the adhesive layer and the polymer film and aluminum foil. The introduction of carboxyl and epoxy functional groups forms a dynamic cross-linking network, which can not only absorb impact energy but also form hydrogen bonds or chemical bonds with each layer, improving the peel strength of the packaging film and enhancing its structural stability and rubbing resistance.

[0021] Preferably, the side of the aluminum foil without the bonding layer is coated with a modified slurry; the modified slurry comprises the following raw materials in parts by weight: 3-5 parts of nano silica; 8-10 parts of sodium alginate and 45-55 parts of deionized water.

[0022] Preferably, the coating amount of the modified slurry is 3-5 g / m². 2 .

[0023] By adopting the above technical solution, if aluminum foil is used as the inner layer and comes into direct contact with food, it may contaminate the contents of the packaging, and food safety cannot be well guaranteed. Therefore, a modified slurry is also coated on the side of the aluminum foil without the bonding layer. Sodium alginate, as a component of the slurry, can not only improve food safety, but also provide a certain preservation effect, extend the shelf life of food, and improve the performance of the obtained packaging film.

[0024] The introduction of nano-silica particles into the modified slurry can, on the one hand, form a tortuous penetration path on the aluminum foil surface, thereby significantly reducing the diffusion rate of oxygen and water vapor; on the other hand, it can fill the pinholes on the aluminum foil surface in a timely manner. Furthermore, the hydrophilicity and swelling properties of sodium alginate also allow it to quickly absorb water and swell when eroded by moisture, partially filling the microcracks and pinholes caused by rubbing, forming a temporary barrier, thereby effectively improving the barrier properties of the packaging film after rubbing.

[0025] Nano-silica, in synergy with sodium alginate, can form a dense network on the surface of aluminum foil, further hindering the penetration of external moisture and oxygen through the micro-defects of the aluminum foil and delaying barrier failure caused by pinhole expansion. Simultaneously, the flexible segments of sodium alginate, combined with the rigid filling of nano-silica particles, can improve the mechanical strength and puncture resistance of the packaging film.

[0026] Secondly, the present invention provides a method for preparing a packaging film, comprising the following process steps: S201. Functional core-shell acrylate particles are added to a polyurethane adhesive, and the mixture is stirred to obtain an adhesive. The adhesive is then applied to the surface of a polymer film at a coating weight of 2.5–3.5 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated to the aluminum foil, and a modified slurry is applied to the other side of the aluminum foil. After drying, the foil is wound up. S203. After winding, the film undergoes a curing process to obtain the packaging film.

[0027] Preferably, the technical effects of the present invention can also be achieved without coating the aluminum foil surface with the modified slurry.

[0028] Preferably, the method for preparing the packaging film includes the following process steps: S201. Functional core-shell acrylate particles are added to a polyurethane adhesive, and the mixture is stirred to obtain an adhesive. The adhesive is then applied to the surface of a polymer film at a coating weight of 2.5–3.5 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated to the aluminum foil, and then wound up; S203. After winding, the film undergoes a curing process to obtain the packaging film.

[0029] Thirdly, the present invention provides a packaging bag prepared using the packaging film obtained above.

[0030] The beneficial effects of this invention are: 1. The adhesive layer of the packaging film of the present invention contains functional core-shell acrylate particles. The functional core-shell acrylate particles are obtained by blending carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles. The adhesive layer prepared can effectively resist cracks and stress concentrations generated under dynamic rubbing, maintain the structural stability of the packaging film. The carboxyl and epoxy groups contained therein can work together to form a dynamic cross-linking network, which can not only effectively disperse stress, but also enhance the interfacial bonding force between the adhesive layer and the polymer film and aluminum foil. The final packaging film has good rubbing resistance and can still have good barrier properties after rubbing.

[0031] 2. The packaging film of the present invention is further coated with a modified slurry on the side of the aluminum foil without the bonding layer. The nano-silica in the modified slurry, together with sodium alginate, can fill the pinholes on the surface of the aluminum foil and the defects that gradually expand after rubbing, thereby improving the rubbing resistance of the packaging film. At the same time, the coating of the modified slurry can also improve the barrier properties of the packaging film, further inhibiting the erosion of the internal food by external moisture and oxygen. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] Preparation Example Preparation Example 1: A functional core-shell acrylate particle was prepared according to the following method: Preparation of carboxylated core-shell acrylate particles: S101. Add 1g sodium dodecyl sulfate to 120g water, mix well, keep the solution temperature at 75℃, add 6g butyl acrylate and 0.05g allyl methacrylate, stir for 15min, add 0.4g ammonium persulfate, stir and react for 60min to obtain seed emulsion; S102. Add 94g of butyl acrylate, 1.6g of sodium dodecyl sulfate and 0.5g of allyl methacrylate to the seed emulsion. After 60min, add 0.1g of ammonium persulfate to induce core layer growth and obtain a core layer emulsion. S103. Add 8g of methacrylic acid, 0.6g of sodium dodecyl sulfate and 25g of methyl methacrylate to the core emulsion. After 30 minutes, add 0.08g of ammonium persulfate to induce shell growth. Keep the solution temperature at 80℃. After 1 hour, cool, filter, freeze, wash, filter and dry to obtain the product.

[0034] An epoxidized core-shell acrylate particle, which differs from the above-mentioned carboxylated core-shell acrylate particles only in that an equal amount of glycidyl methacrylate is used instead of methacrylic acid.

[0035] Carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles obtained above were weighed out at a mass ratio of 1.5:1 and mixed to obtain functional core-shell acrylate particles.

[0036] Preparation Example 2, a functional core-shell acrylate particle, differs from Preparation Example 1 only in that, in the preparation of carboxylated core-shell acrylate particles, the amount of methacrylic acid added is 5g and the amount of methyl methacrylate added is 30g; in the preparation of epoxidized core-shell acrylate particles, the amount of glycidyl methacrylate added is 5g and the amount of methyl methacrylate added is 30g.

[0037] Preparation Example 3, a functional core-shell acrylate particle, differs from Preparation Example 1 only in that, in the preparation of carboxylated core-shell acrylate particles, the amount of methacrylic acid added is 10g and the amount of methyl methacrylate added is 20g; in the preparation of epoxidized core-shell acrylate particles, the amount of glycidyl methacrylate added is 10g and the amount of methyl methacrylate added is 20g.

[0038] Preparation Example 4: A functional core-shell acrylate particle. The only difference from Preparation Example 1 is that the carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles obtained in Preparation Example 1 were weighed out at a mass ratio of 1:1 and mixed to obtain the functional core-shell acrylate particle.

[0039] Preparation Example 5: A functional core-shell acrylate particle. The only difference from Preparation Example 1 is that the carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles obtained in Preparation Example 1 were weighed at a mass ratio of 2:1 and mixed to obtain the functional core-shell acrylate particle.

[0040] Preparation Example 6: A functional core-shell acrylate particle. The only difference from Preparation Example 1 is that the carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles obtained in Preparation Example 1 were weighed out at a mass ratio of 0.5:1 and mixed to obtain the functional core-shell acrylate particle.

[0041] Preparation Example 7: A functional core-shell acrylate particle. The only difference from Preparation Example 1 is that the carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles obtained in Preparation Example 1 were weighed at a mass ratio of 2.5:1 and mixed to obtain the functional core-shell acrylate particle.

[0042] Preparation Example 8: A functional core-shell acrylate particle, which differs from Preparation Example 1 only in that the functional core-shell acrylate particle is the carboxylated core-shell acrylate particle obtained in Preparation Example 1.

[0043] Preparation Example 9: A functional core-shell acrylate particle, which differs from Preparation Example 1 only in that the functional core-shell acrylate particle is the epoxidized core-shell acrylate particle obtained in Preparation Example 1.

[0044] Preparation Example 10: A core-shell acrylate particle was prepared according to the following method: S101. Add 1g sodium dodecyl sulfate to 120g water, mix well, keep the solution temperature at 75℃, add 6g butyl acrylate and 0.05g allyl methacrylate, stir for 15min, add 0.4g ammonium persulfate, stir and react for 60min to obtain seed emulsion; S102. Add 94g of butyl acrylate, 1.6g of sodium dodecyl sulfate and 0.5g of allyl methacrylate to the seed emulsion. After 60min, add 0.1g of ammonium persulfate to induce core layer growth and obtain a core layer emulsion. S103. Add 0.6 g sodium dodecyl sulfate and 30 g methyl methacrylate to the core emulsion. After 30 min, add 0.08 g ammonium persulfate to induce shell growth. Keep the solution temperature at 80 °C. After 1 h, cool, filter, freeze, wash, filter again and dry to obtain the product.

[0045] Example Example 1: A packaging film prepared according to the following process steps: S201. The functional core-shell acrylate particles prepared in Preparation Example 1 were added to a polyether-type polyurethane adhesive at an addition amount of 10 wt%. The mixture was stirred to obtain an adhesive. The adhesive was then applied to the surface of a polyethylene terephthalate film (average thickness of 12 μm) at an application rate of 3 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated with aluminum foil (average thickness 7μm), and then wound up; S203. After winding, the film undergoes a curing process at a temperature of 60°C for 40 hours to obtain the packaging film.

[0046] Example 2, a packaging film, differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Example 2 are used instead of the functional core-shell acrylate particles prepared in Example 1.

[0047] Example 3, a packaging film, differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Example 3 are used instead of the functional core-shell acrylate particles prepared in Example 1.

[0048] Example 4, a packaging film, differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Example 4 are used instead of the functional core-shell acrylate particles prepared in Example 1.

[0049] Example 5, a packaging film, differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Example 5 are used instead of the functional core-shell acrylate particles prepared in Example 1.

[0050] Example 6, a packaging film, differs from Example 1 only in that the amount of functional core-shell acrylate particles prepared in Example 1 added is 8 wt%, and the coating amount is 3.5 g / m. 2 .

[0051] Example 7, a packaging film, differs from Example 1 only in that the amount of functional core-shell acrylate particles prepared in Example 1 added is 12 wt%, and the coating amount is 2.5 g / m³. 2 .

[0052] Example 8: A packaging film prepared according to the following process steps: S201. The functional core-shell acrylate particles prepared in Preparation Example 1 were added to a polyether-type polyurethane adhesive at an addition amount of 10 wt%. The mixture was stirred to obtain an adhesive. The adhesive was then applied to the surface of a polyethylene terephthalate film (average thickness of 12 μm) at an application rate of 3 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated with aluminum foil (average thickness 7 μm). 10 parts sodium alginate and 4 parts nano-silica (average particle size 50 nm) are added to 50 parts deionized water and ultrasonically dispersed to obtain a modified slurry. The modified slurry is then coated onto the other side of the aluminum foil at a coating amount of 4 g / m². 2 Then roll it up; S203. After winding, the film undergoes a curing process at a temperature of 60°C for 40 hours to obtain the packaging film.

[0053] Example 9, a packaging film, differs from Example 8 only in that the raw materials of the modified slurry include 45 parts deionized water, 8 parts sodium alginate and 3 parts nano silica.

[0054] Example 10, a packaging film, differs from Example 8 only in that the raw materials of the modified slurry include 50 parts deionized water, 10 parts sodium alginate and 1 part nano silica.

[0055] Example 11, a packaging film, differs from Example 8 only in that the raw materials of the modified slurry include 50 parts deionized water, 10 parts sodium alginate and 7 parts nano silica.

[0056] Example 12, a packaging film, differs from Example 8 only in that the raw materials of the modified slurry include 50 parts of deionized water and 10 parts of sodium alginate.

[0057] Comparative Example Comparative Example 1 is a packaging film that differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Preparation Example 6 are used instead of the functional core-shell acrylate particles prepared in Preparation Example 1.

[0058] Comparative Example 2 is a packaging film that differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Preparation Example 7 are used instead of the functional core-shell acrylate particles prepared in Preparation Example 1.

[0059] Comparative Example 3 is a packaging film that differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Preparation Example 8 are used instead of the functional core-shell acrylate particles prepared in Preparation Example 1.

[0060] Comparative Example 4 is a packaging film that differs from Example 1 only in that an equal amount of functional core-shell acrylate particles prepared in Preparation Example 9 are used instead of the functional core-shell acrylate particles prepared in Preparation Example 1.

[0061] Comparative Example 5 is a packaging film that differs from Example 1 only in that an equal amount of core-shell acrylate particles prepared in Preparation Example 10 are used instead of the functional core-shell acrylate particles prepared in Preparation Example 1.

[0062] Comparative Example 6, a packaging film, differs from Example 1 only in that the amount of functional core-shell acrylate particles added in Preparation Example 1 is 5 wt%.

[0063] Comparative Example 7, a packaging film, differs from Example 1 only in that the amount of functional core-shell acrylate particles added in Preparation Example 1 is 15 wt%.

[0064] Comparative Example 8: A packaging film prepared according to the following process steps: S201. Apply a polyether-type polyurethane adhesive to the surface of a polyethylene terephthalate film (average thickness 12 μm) at an application rate of 3 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated with aluminum foil (average thickness 7μm), and then wound up; S203. After winding, the film undergoes a curing process at a temperature of 60°C for 40 hours to obtain the packaging film.

[0065] Performance testing 1. Rub resistance test: According to the relevant records in ASTM F392 / F392M-11 (2015) "Rubbing resistance test method for flexible barrier materials", the packaging films obtained in the examples and comparative examples were rubbed. Specifically, the test samples were rubbed 270 times within 6 minutes.

[0066] According to the relevant records in GB / T 28118-2011 "Plastic and Aluminum Foil Composite Films and Bags for Food Packaging", the oxygen permeability of the packaging film before and after rubbing was measured, and then the oxygen permeability enhancement rate (%) was calculated. The oxygen permeability enhancement rate was calculated as follows:

[0067] 2. Peel strength test: According to the relevant records in GB / T 28118-2011 "Plastic and aluminum foil composite films and bags for food packaging", the peel strength of the packaging films obtained in the examples and comparative examples was calculated.

[0068] The results of the above experiments are shown in Table 1: Table 1 Performance test results

[0069] According to Table 1, combined with Examples 1 and 8, it can be seen that the oxygen permeation rate of Example 8 has decreased, indicating that the oxygen barrier performance of Example 8 decreased less after the rubbing action, and the barrier performance increased compared to Example 1. The reason is that in Example 8, a modified slurry was also coated on the side of the aluminum foil without the adhesive layer. The nano silica in the modified slurry, together with sodium alginate, can fill the pinholes on the surface of the aluminum foil and the defects that gradually expand after the rubbing action, effectively improving the rubbing resistance and barrier performance of the packaging film.

[0070] Combining Examples 8 and 10-12, it can be seen that the oxygen permeation rate of Examples 10-12 is higher than that of Example 8, indicating that the oxygen permeation rate of Examples 10-12 increases more significantly after the rubbing action compared to Example 8, while the rubbing resistance decreases. This is because the only difference between Examples 10-12 and Example 8 is the adjustment of the amount of nano-silica added to the modified slurry. In Example 10, the content of nano-silica was reduced, thus decreasing the filling effect of the modified slurry on aluminum foil defects and the enhancement of barrier properties. In Example 12, no nano-silica was added, resulting in a more significant performance decrease. In Example 11, the amount of nano-silica added was increased. However, the excessive addition of nanoparticles increases the possibility of agglomeration between nano-silica particles in the modified slurry. Agglomeration, in turn, can cause stress concentration, which is detrimental to increasing the rubbing resistance of the packaging film.

[0071] Based on Examples 1 and Comparative Examples 1-5, it can be seen that the oxygen permeation rate of Comparative Examples 1-5 is significantly increased compared to Example 1, while the peel strength is decreased compared to Example 1. This indicates that the tear resistance of Comparative Examples 1-5 is lower than that of Example 1. The reason for this is that Comparative Examples 1-5 mainly focused on the functionalization of the core-shell acrylate particles. In Comparative Example 1, the amount of carboxylated core-shell acrylate particles added was reduced, which limited the crosslinking reaction between carboxyl and epoxy groups, reduced the interfacial bonding force between the adhesive and the aluminum foil, and indirectly affected the tear resistance of the packaging film and the bonding force between layers. Correspondingly, Comparative Example 4 did not add carboxylated core-shell acrylate particles, and the corresponding performance decline was more significant. In Comparative Example 2, the amount of carboxylated core-shell acrylate particles added was increased, and the crosslinking density increased, which was not conducive to improving the toughness of the adhesive layer, leading to stress concentration, brittle fracture, and decreased tear resistance. In Comparative Example 3, only carboxylated core-shell acrylate particles were added, without the cross-linking effect of epoxy groups, resulting in a decrease in the improvement of rub resistance and a decrease in peel strength.

[0072] Based on Examples 1 and Comparative Examples 6 to 8, it can be seen that the oxygen permeation rate of Comparative Examples 6 to 8 is significantly increased compared to Example 1, while the peel strength is decreased compared to Example 1. This indicates that the tumbling resistance of Comparative Examples 6 to 8 is lower than that of Example 1. The reason for this is that Comparative Examples 6 to 8 changed the amount of functional core-shell acrylate particles added. If the amount added is too small, the modification effect will not be obvious, while if the amount added is too large, it will lead to excessive crosslinking density and particle agglomeration, which will result in a decrease in material performance.

[0073] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0074] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A packaging film, characterized in that, The packaging film comprises at least a polymer film, an adhesive layer, and an aluminum foil; the adhesive layer is located between the polymer film and the aluminum foil. The adhesive layer comprises 8-12 wt% of functional core-shell acrylate particles; the functional core-shell acrylate particles comprise carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles in a mass ratio of (1-2):

1.

2. The packaging film according to claim 1, characterized in that, The adhesive layer also includes polyurethane adhesives; the polyurethane adhesives include one or a combination of polyether polyurethane and polyester polyurethane.

3. The packaging film according to claim 1, characterized in that, The raw materials for the carboxylated core-shell acrylate particles include butyl acrylate, methyl methacrylate and carboxyacrylate monomers in a mass ratio of 100:(20-30):(5-10); the raw materials for the epoxidized core-shell acrylate particles include butyl acrylate, methyl methacrylate and epoxy acrylate monomers in a mass ratio of 100:(20-30):(5-10).

4. The packaging film according to claim 3, characterized in that, The carboxyacrylate monomer includes one or more combinations of methacrylic acid, methacryloyloxyethyl succinate, and methacryloyloxyethyl maleic acid monoester; the epoxyacrylate monomer includes one or more combinations of glycidyl methacrylate, glycidyl acrylate, and phenyl glycidyl ether acrylate.

5. The packaging film according to claim 3, characterized in that, The functional core-shell acrylate particles were prepared according to the following method: S101. Add emulsifier to water, mix well, keep the solution temperature at 70-80℃, add 5-8wt% butyl acrylate and crosslinking agent, stir for 10-20min, add initiator, stir reaction for 60-90min to obtain seed emulsion; S102. Add the remaining butyl acrylate to the seed emulsion, along with the emulsifier and crosslinking agent. After 40-60 minutes, add the initiator to induce core layer growth and obtain a core layer emulsion. S103. Add carboxylated acrylic monomer or epoxy acrylic monomer, emulsifier and methyl methacrylate to the core emulsion. After 30-40 min, add an initiator to initiate shell growth. Keep the solution temperature at 75-85℃. After 1-2 h, cool, filter, freeze, wash, filter and dry to obtain carboxylated core-shell acrylate particles or epoxidized core-shell acrylate particles. S104. Functional core-shell acrylate particles are obtained by mixing carboxylated core-shell acrylate particles and epoxidized core-shell acrylate particles.

6. The packaging film according to claim 5, characterized in that, The emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl sulfonate; the crosslinking agent includes one or more of allyl methacrylate, 1,4-butanediol diacrylate, ethylene glycol diacrylate, and trimethylolpropane triacrylate; and the initiator includes one or more of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

7. The packaging film according to claim 1, characterized in that, The side of the aluminum foil without the bonding layer is coated with a modified slurry; the modified slurry comprises the following raw materials in parts by weight: 3-5 parts of nano silica, 8-10 parts of sodium alginate and 45-55 parts of deionized water.

8. The packaging film according to claim 7, characterized in that, The coating amount of the modified slurry is 3-5 g / m. 2 .

9. A method for preparing a packaging film according to any one of claims 1 to 8, characterized in that, The process includes the following steps: S201. Functional core-shell acrylate particles are added to a polyurethane adhesive, and the mixture is stirred to obtain an adhesive. The adhesive is then applied to the surface of a polymer film at a coating weight of 2.5–3.5 g / m². 2 This forms an adhesive layer; S202. The adhesive layer is then laminated to the aluminum foil, and a modified slurry is applied to the other side of the aluminum foil. After drying, the foil is wound up. S203. After winding, the film undergoes a curing process to obtain the packaging film.

10. A packaging bag, characterized in that, It is prepared using the packaging film according to any one of claims 1 to 8.

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