Aluminum-plastic composite film and preparation method thereof

Abstract

The application discloses an aluminum-plastic composite film and a preparation method thereof. The aluminum-plastic composite film comprises an outer layer, a glue layer, an anticorrosion layer, an aluminum foil layer, an anticorrosion layer, a bonding layer and a heat-sealing layer. The glue layer comprises modified polyurethane, and the modified polyurethane comprises the following components according to weight parts: component A, 2-40 parts of polyhydric alcohol, 0.5-2 parts of an additive; component B, 10-60 parts of modified prepolymer, 2-4 parts of an additive and 1-5 parts of a filler. The modified prepolymer in the component B is obtained by using prepolymer grafted polymer microspheres, the prepolymer is obtained by synthesizing isocyanate and polyhydric alcohol, and the polymer microspheres comprise polymer microspheres of one or more groups of a silicon group and a double bond group. The glue layer prepared by the application can greatly improve the water resistance and heat resistance of the aluminum-plastic composite film, reduces the delamination phenomenon of the aluminum-plastic composite film and prolongs the service life of the aluminum-plastic composite film.

Description

Technical Field

[0001] This application relates to the field of composite films, and in particular to an aluminum-plastic composite film and its preparation method. Background Technology

[0002] In the field of lithium batteries, separator materials are often used to isolate the positive and negative electrodes of lithium batteries to prevent the positive and negative electrode materials in the battery from coming into direct contact and causing a short circuit.

[0003] Currently, aluminum-plastic composite film is commonly used as a separating material. Aluminum-plastic composite film is a material composed of aluminum foil and plastic film, which has good thermal stability, puncture resistance, strength and electrolyte wetting properties.

[0004] However, when aluminum foil and plastic film are laminated by heat sealing or adhesive bonding, prolonged exposure to air can cause moisture penetration, leading to adhesive failure, which weakens the adhesion between the aluminum foil and plastic film, resulting in delamination or peeling. Summary of the Invention

[0005] To reduce the problem of delamination in aluminum-plastic composite films, this application provides an aluminum-plastic composite film and its preparation method.

[0006] In a first aspect, an aluminum-plastic composite film includes an outer layer, an adhesive layer, an anti-corrosion layer, an aluminum foil layer, an adhesive layer, and a heat-sealing layer;

[0007] The adhesive layer includes modified polyurethane, which, by weight, comprises the following components:

[0008] Component A: 2-40 parts polyol, 0.5-2 parts primary auxiliary agent;

[0009] Component B includes 10-60 parts of modified prepolymer, 2-4 parts of secondary additive, and 1-5 parts of filler;

[0010] The modified prepolymer in component B is obtained by grafting prepolymer onto polymer microspheres, and the prepolymer is synthesized from isocyanate and polyol.

[0011] Typically, but not limitingly, the polyol in component A is one of polyethylene terephthalate, polybutylene succinate, or polycaprolactone.

[0012] By adopting the above technical solution, after the prepolymer is formed, polymer microspheres are grafted onto it. These microspheres exhibit good compatibility with polyurethane and can be uniformly dispersed in the adhesive layer. The microspheres also possess good chemical stability, improving the heat and water resistance of the adhesive. Furthermore, the microspheres have good biocompatibility and are easily modified, facilitating further modification to introduce groups such as epoxy groups, double bonds, or silicon groups to enhance the heat and water resistance of the adhesive. The microspheres also improve the compatibility between the polyurethane and the outer layer (nylon film), further enhancing the adhesion between the outer layer and the adhesive layer and reducing delamination.

[0013] Preferably, the first additive includes one or more of leveling agents, defoamers, antioxidants, and dispersants, and the second additive includes one or more of leveling agents, defoamers, antioxidants, and dispersants.

[0014] By adopting the above technical solutions, the above additives can improve the water resistance and heat resistance of the adhesive layer, thereby extending the service life of the aluminum-plastic composite film.

[0015] Preferably, the filler comprises one or more of kaolin, montmorillonite, silica gel, or nanomaterials.

[0016] By employing the above technical solutions, kaolin, montmorillonite, and silica gel all exhibit good compatibility with polyurethane and possess a large specific surface area. This reduces the contact between urethane groups (easily hydrolyzed groups within polyurethane) and moisture per unit volume, thereby improving the water resistance of polyurethane. These three materials also enhance the mechanical properties of polyurethane, and due to their large specific surface area, they increase the frictional resistance between molecular chains, thus improving the adhesive's tackiness and reducing peeling between the outer layer and the anti-corrosion layer.

[0017] Preferably, the polymer microspheres are organic composite microspheres, which, by weight, comprise the following components: 22-45 parts polymethyl methacrylate, 8-20 parts acrylic acid, 12-16 parts pentaerythritol triallyl ether, and 1-2 parts crosslinking agent.

[0018] Typically, but not limitingly, there are no special requirements for the crosslinking agent in this application; commonly used crosslinking agents in the art, such as azobisisobutyronitrile, can be used.

[0019] By adopting the above technical solution, polymethyl methacrylate (PMMA), acrylic acid, and pentaerythritol triallyl ether (PTE) are selected as raw materials for the composite microspheres. PMMA has good water absorption and heat resistance, which can improve the overall water resistance and heat resistance of polyurethane. Acrylic acid also has good heat resistance, and it can further condense with polyurethane during use, reducing the number of hydrolyzable groups and improving its water resistance. Pentaerythritol triallyl ether also has good heat resistance, and it can further condense with polyurethane, reducing the number of easily hydrolyzable groups in polyurethane and improving its water resistance. Pentaerythritol triallyl ether also has high viscosity, which can improve the adhesion of polyurethane adhesives.

[0020] Furthermore, the organic composite microspheres prepared from these three materials exhibit good compatibility with polyurethane and can improve the compatibility between polyurethane and the outer layer (nylon layer), thereby enhancing adhesion. The organic composite microspheres possess strong hydrophilic properties, absorbing moisture from the outside and forming a hydrogel structure that provides support for the polyurethane, thus improving its water resistance. After absorbing a certain amount of water, the organic composite microspheres form a densely packed structure, restricting water shear flow, increasing the overall viscosity of the polyurethane, and forming a hydrophobic layer inside, reducing water penetration. This improves both the water resistance and the bonding strength of the polyurethane. The packed structure also fills the spatial structure of the polyurethane, thereby improving its mechanical strength and thermal stability.

[0021] Preferably, the polymer microspheres are modified organic composite microspheres grafted with vegetable oil. The modified organic composite microspheres, by weight, comprise the following components: 22-45 parts polymethyl methacrylate, 8-20 parts acrylic acid, 12-16 parts pentaerythritol triallyl ether, 1-2 parts crosslinking agent, 8-16 parts vegetable oil, and 0.5-1 parts acid catalyst.

[0022] Typically, but not limitingly, the vegetable oil used is one of castor oil, soybean oil, or rapeseed oil. This application does not have specific requirements for the acid catalyst; commonly used acid catalysts in the art, such as cobalt naphthenate, can be used.

[0023] By employing the above-mentioned technical solution, under the action of an acid catalyst, the hydroxyl groups on vegetable oil can undergo esterification with the carboxyl groups on organic composite microspheres, thereby grafting vegetable oil onto the organic composite microspheres to form modified organic composite microspheres. Taking castor oil as an example, after grafting onto the organic composite microspheres, it can lower the glass transition temperature of the organic composite microspheres, improve heat resistance, and further improve the toughness and flexibility of the organic composite microspheres, enhance the uniformity of crosslinking and the variability of the structure, thereby improving the heat resistance and water resistance of polyurethane.

[0024] Preferably, the method for preparing the polymer microspheres comprises the following steps:

[0025] Preparation of organic composite microspheres: Polymethyl methacrylate was dissolved in dichloromethane, then acrylic acid, pentaerythritol triallyl ether and crosslinking agent were added, and the reaction was carried out at 75-85℃ for 40-50 min, and then the temperature was lowered to 50-60℃ and maintained for 50-70 min to obtain organic composite microspheres.

[0026] Preparation of modified organic composite microspheres: Vegetable oil was added to the organic composite microspheres, an acid catalyst was added, and the mixture was reacted at 70-80℃ for 10-20 min. Then, dichloromethane was removed to obtain the modified organic composite microspheres.

[0027] By adopting the above technical solution, organic composite microspheres are first prepared to improve the conversion rate of the microspheres, and then grafting is performed to further improve the surface structure and properties of the microspheres, thereby improving the heat resistance and water resistance of polyurethane.

[0028] Preferably, the filler is nano-titanium dioxide.

[0029] By employing the above technical solution, nano-titanium dioxide can also form cross-linking points between polyurethane and organic composite microspheres, limiting the hydrolysis and thermal degradation of polyurethane. Nano-titanium dioxide also has good hydrophilicity, which can accelerate the curing of polyurethane and improve the adhesive effect of the adhesive layer. More importantly, the addition of nano-titanium dioxide can improve the phase separation degree of polyurethane, thereby inhibiting the hydrolysis reaction and improving the water resistance of polyurethane.

[0030] However, since nano-titanium dioxide is a nanoparticle, direct grafting with polyurethane may lead to a strong agglomeration reaction. Furthermore, the urethane formed after grafting nano-titanium dioxide with isocyanate has poor thermal stability and is easily hydrolyzed. However, after modifying the prepolymer with organic composite microspheres, the organic composite microspheres, with their large specific surface area and more active groups on their surface, can adsorb onto the nano-titanium dioxide and distribute it evenly on the surface of each microsphere, thus reducing its agglomeration effect. As the organic composite microspheres are more evenly distributed within the polyurethane, the thermal stability and water resistance of the polyurethane are synergistically improved.

[0031] Preferably, the modified prepolymer comprises, by weight, the following components: 30-40 parts polyol, 10-20 parts isocyanate, 4-8 parts polymer microspheres, 1-3.6 parts chain extender, and 0.01-0.03 parts catalyst.

[0032] Typically, but not limitingly, the polyol is a polyester polyol or a bio-based polyol, the isocyanate is one of 1,5-pentanediisocyanate, dimer diisocyanate or lysine diisocyanate, the catalyst is an organotin catalyst, and the chain extender is 1,4-butanediol or dimethylolpropionic acid.

[0033] Preferably, the modified prepolymer is prepared according to the following steps:

[0034] Polyol, isocyanate, catalyst and chain extender are reacted at 75-85℃ for 5-7h to obtain prepolymer; after the prepolymer cools to 20-30℃, polymer microspheres are added and sheared at 2000-3000r / min for 10-30min to obtain modified prepolymer.

[0035] By adopting the above technical solution and setting the above parameters, a modified prepolymer with good yield can be obtained, and the reaction conditions are mild, thus saving costs.

[0036] Secondly, a method for preparing an aluminum-plastic composite film, comprising the following steps:

[0037] An aluminum-plastic composite film is obtained by heat-sealing the outer layer, adhesive layer, anti-corrosion layer, aluminum foil layer, adhesive layer, and heat-sealing layer.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. This application involves introducing organic composite microspheres into polyurethane. The organic composite microspheres form more cross-linked structures with the polyurethane and reduce the contact between unstable, easily hydrolyzed groups in the polyurethane per unit volume and water, thereby reducing water penetration. At the same time, it improves the stability of the polyurethane, increases the service life and strength of the adhesive layer, reduces the occurrence of delamination, and thus extends the service life of the aluminum-plastic composite film and saves replacement costs.

[0040] 2. The organic composite microspheres are further modified with vegetable oil and combined with nano-titanium dioxide to synergistically improve the heat resistance and water resistance of polyurethane, and can solve the problems of severe agglomeration of nano-titanium dioxide and poor effect of direct grafting of vegetable oil onto polyurethane that existed in the field before. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the embodiments.

[0042] Preparation Example 1-1: A polymer microsphere was prepared using the following steps:

[0043] Preparation of organic composite microspheres: 34g of polymethyl methacrylate was dissolved in 200mL of dichloromethane, and then 14g of acrylic acid, 14g of pentaerythritol triallyl ether and 1.5g of azobisisobutyronitrile were added. The mixture was reacted at 80℃ for 45min, and then the temperature was lowered to 55℃ and maintained for 60min to obtain organic composite microspheres.

[0044] Preparation of modified organic composite microspheres: 12g castor oil was added to the organic composite microspheres, 0.8g cobalt naphthenate was added, and the mixture was reacted at 75℃ for 15min. Then, dichloromethane was removed to obtain the modified organic composite microspheres.

[0045] Preparation Examples 1-2: A polymer microsphere was prepared using the following steps:

[0046] Preparation of organic composite microspheres: 22g of polymethyl methacrylate was dissolved in 200mL of dichloromethane, and then 8g of acrylic acid, 12g of pentaerythritol triallyl ether and 1g of azobisisobutyronitrile were added. The mixture was reacted at 75℃ for 50min, and then the temperature was lowered to 50℃ and maintained for 70min to obtain organic composite microspheres.

[0047] Preparation of modified organic composite microspheres: 8g castor oil was added to the organic composite microspheres, 0.5g cobalt naphthenate was added, and the mixture was reacted at 70℃ for 20min. Then, dichloromethane was removed to obtain the modified organic composite microspheres.

[0048] Preparation Examples 1-3: A polymer microsphere was prepared using the following steps:

[0049] Preparation of organic composite microspheres: 45g of polymethyl methacrylate was dissolved in 200mL of dichloromethane, and then 20g of acrylic acid, 16g of pentaerythritol triallyl ether and 2g of azobisisobutyronitrile were added. The mixture was reacted at 85℃ for 40min, and then the temperature was lowered to 60℃ and maintained for 50min to obtain organic composite microspheres.

[0050] Preparation of modified organic composite microspheres: 16g castor oil was added to the organic composite microspheres, 1g cobalt naphthenate was added, and the mixture was reacted at 80℃ for 10min. Then, dichloromethane was removed to obtain the modified organic composite microspheres.

[0051] Preparation Examples 1-4: A polymer microsphere was prepared using the following steps:

[0052] Preparation of organic composite microspheres: 34g of polymethyl methacrylate was dissolved in 200mL of dichloromethane, and then 14g of acrylic acid, 14g of pentaerythritol triallyl ether and 1.5g of azobisisobutyronitrile were added. The mixture was reacted at 80℃ for 45min, and then the temperature was lowered to 55℃ and maintained for 60min to obtain organic composite microspheres.

[0053] Preparation Examples 1-5: A polymer microsphere, using methacrylate polymer microspheres.

[0054] Preparation Example 2-1, a modified prepolymer, was prepared using the following steps:

[0055] 35g of polypropylene glycol, 15g of dimer diisocyanate, 0.02g of dibutyltin dilaurate and 2.3g of 1,4-butanediol were reacted at 80℃ for 6h to obtain a prepolymer; after the prepolymer cooled to 25℃, polymer microspheres were added and sheared at 2500r / min for 20min to obtain a modified prepolymer.

[0056] Among them, the polymer microspheres are the modified organic composite microspheres prepared in Example 1-1.

[0057] Preparation Example 2-2, a modified prepolymer, prepared using the following steps:

[0058] 40g of polypropylene glycol, 20g of dimer diisocyanate, 0.03g of dibutyltin dilaurate and 3.6g of 1,4-butanediol were reacted at 85℃ for 5h to obtain a prepolymer; after the prepolymer cooled to 20℃, 8g of polymer microspheres were added and sheared at 3000r / min for 10min to obtain a modified prepolymer.

[0059] Among them, the polymer microspheres are the modified organic composite microspheres prepared in Examples 1-2.

[0060] Preparation Example 2-3, a modified prepolymer, was prepared using the following steps:

[0061] Take 30g of polypropylene glycol, 10g of dimer diisocyanate, 0.01g of dibutyltin dilaurate and 1g of 1,4-butanediol and react them at 75℃ for 7h to obtain a prepolymer; after the prepolymer cools down to 30℃, add 4g of polymer microspheres and shear disperse at 2000r / min for 30min to obtain a modified prepolymer.

[0062] Among them, the polymer microspheres are the modified organic composite microspheres prepared in Examples 1-3.

[0063] Preparation Example 2-4 is a modified prepolymer, which differs from Preparation Example 2-1 in that the polymer microspheres are replaced with the organic composite microspheres of Preparation Example 1-4.

[0064] Preparation Example 2-5 is a modified prepolymer, which differs from Preparation Example 2-1 in that the polymer microspheres used are those of Preparation Example 1-5.

[0065] Preparation Examples 2-6: A modified prepolymer was prepared by the following steps: 35g of polypropylene glycol, 15g of dimer diisocyanate, 0.02g of dibutyltin dilaurate and 2.3g of 1,4-butanediol were reacted at 80°C for 6h to obtain the modified prepolymer.

[0066] Preparation Examples 2-7: A modified prepolymer was prepared using the following steps:

[0067] Preparation of prepolymer: 35g polypropylene glycol, 15g dimer diisocyanate, 0.02g dibutyltin dilaurate, 2.3g 1,4-butanediol and 3g castor oil were reacted at 80℃ for 6h to obtain prepolymer; after the prepolymer was cooled to 25℃, polymer microspheres were added and sheared and dispersed at 2500r / min for 20min to obtain modified prepolymer.

[0068] Among them, the polymer microspheres are the organic composite microspheres prepared in Examples 1-4.

[0069] Preparation Example 3-1: A modified polyurethane was prepared using the following steps:

[0070] Preparation of component A: Take 21g of polyethylene terephthalate, heat to 100℃ and stir for 15min, then add 1.3g of defoamer, apply vacuum negative pressure of -0.1MPa, maintain 100℃ and stir to dehydrate for 30min to obtain component A.

[0071] Preparation of component B: Take 35g of modified prepolymer, add 1g of antioxidant and 1g of dispersant, mix and stir for 12min;

[0072] Then add 3g of nano titanium dioxide and stir for 45 minutes;

[0073] Turn on the vacuum pump, set the negative pressure to -0.1 MPa, and stir and degas for 20 minutes;

[0074] Component B was obtained.

[0075] The modified prepolymer was derived from Preparation Example 2-1.

[0076] In some specific embodiments, polymethyl methacrylate can also be replaced with an equal amount of polybutylene succinate or polycaprolactone.

[0077] Preparation Example 3-2, a modified polyurethane, differs from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-2.

[0078] Preparation Example 3-3, a modified polyurethane, differs from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-3.

[0079] Preparation Example 3-4, a modified polyurethane, differs from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-4.

[0080] Preparation Example 3-5, a modified polyurethane, differs from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-5.

[0081] Preparation Examples 3-6, a modified polyurethane, differ from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-6.

[0082] Preparation Example 3-7, a modified polyurethane, differs from Preparation Example 3-1 in that nano-titanium dioxide is replaced with an equal amount of kaolin.

[0083] Preparation Examples 3-8. A modified polyurethane, which differs from Preparation Examples 3-5 in that nano-titanium dioxide is replaced with an equal amount of kaolin.

[0084] Preparation Examples 3-9, a modified polyurethane, differ from Preparation Examples 3-6 in that nano-titanium dioxide is replaced with an equal amount of kaolin.

[0085] Preparation Example 3-10, a modified polyurethane, differs from Preparation Example 3-1 in that the modified prepolymer is derived from Preparation Example 2-7. Example

[0086] Example 1: An aluminum-plastic composite film is prepared using the following steps:

[0087] An aluminum-plastic composite film is obtained by heat-sealing the outer layer, adhesive layer, anti-corrosion layer, aluminum foil layer, adhesive layer, and heat-sealing layer.

[0088] The outer layer is a polyamide film layer with a thickness of 15-30 μm; the adhesive layer is obtained by coating with modified polyurethane as described in Preparation Example 3-1 of this application, with a thickness of 2-5 μm; the anti-corrosion layer is an anti-corrosion layer treated with trivalent chromium passivating agent; the aluminum foil layer is O-state 8021 aluminum foil with a thickness of 30-60 μm; the bonding layer is obtained by coating with modified polyolefin adhesive with a thickness of 2-5 μm; and the heat-sealing layer is a cast polypropylene film with a thickness of 30-80 μm.

[0089] Example 2, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the modified polyurethane prepared in Example 3-2.

[0090] Example 3, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Example 3-3.

[0091] Example 4, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Examples 3-4.

[0092] Example 5, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Examples 3-5.

[0093] Example 6, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Examples 3-7.

[0094] Example 7, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Examples 3-8.

[0095] Example 8 is an aluminum-plastic composite film, which differs from Example 1 in that the modified polyurethane used is the modified polyurethane prepared in Examples 3-10.

[0096] Comparative Example 1, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Examples 3-6.

[0097] Comparative Example 2, an aluminum-plastic composite film, differs from Example 1 in that the modified polyurethane used is the same as that used in Preparation Examples 3-9.

[0098] Comparative Example 3, an aluminum-plastic composite film, was prepared using the following steps:

[0099] Aluminum foil measuring 300m in length and 520mm in width was passed sequentially through three stages of deionized water cleaning tanks and a 120℃ drying oven at a linear speed of 40m / min to remove foreign matter and grease from its surface. After drying, the aluminum foil underwent plasma treatment at 3000V to further remove grease and create a rough surface that increases its absorbency.

[0100] Take 50g of the passivation solution stock solution and dilute it with 12.5g of pure water to prepare a passivation solution with a pH value of 2-5. Apply the prepared passivation solution to both sides of the aluminum foil using a screen roller, preferably a 200-mesh roller. Dry the aluminum foil coated with the passivation solution at a temperature of 180℃ to form a dense, inert oxide layer on the surface of the aluminum foil.

[0101] Add 80g of ethyl acetate solvent to 20g of outer layer adhesive raw material to dissolve and dilute to prepare outer layer adhesive liquid. Apply the outer layer adhesive liquid to one side of the aluminum foil to form a 4um thick outer adhesive layer. After baking at a high temperature of 90°C, the outer layer film is laminated to the outer adhesive layer under a pressure of 0.3MPa to form an adhesive layer.

[0102] Add 80g of ethyl acetate solvent to 90g of inner adhesive layer raw material and mix thoroughly. Then apply the inner layer adhesive to the other side of the aluminum foil to form a 4µm thick inner adhesive layer. After baking at 90°C, the heat-sealing layer film is laminated to the inner adhesive layer under a pressure of 0.3MPa to form a heat-sealing layer, thus obtaining an aluminum-plastic composite film.

[0103] The performance of the aluminum-plastic composite films obtained in Examples 1-8 and Comparative Examples 1-3 was tested. The test standards were all in T / CIAPS0005—2018 "Aluminum-plastic Composite Film for Lithium-ion Batteries". Each example and comparative example was tested 6 times and the average value was taken.

[0104] Test 1: Resistance to damp heat: After stamping a 130 mm × 240 mm sample under a surface pressure of 0.15 MPa to 0.3 MPa, the sample was placed at a temperature of (60±2)℃ and a relative humidity of (90±5)% for 72 h and 96 h. The sample was then removed and allowed to cool naturally to room temperature. The appearance of the sample was then checked and recorded. The results are shown in Table 1.

[0105] Experiment 2: Heat resistance: Samples with dimensions of 130 mm × 240 mm were stamped under a surface pressure of 0.15 MPa to 0.3 MPa. The samples were then placed at a temperature of (85±2)℃ for 24 h and 48 h, and then naturally cooled to room temperature. The appearance of the samples was checked and recorded. The results are shown in Table 1.

[0106] Experiment 3: Peeling force: The peeling was conducted according to the provisions of GB / T 8808-1988 except for "6 Test speed". A universal testing machine with an accuracy of 0.5 grade was used to perform the peeling at a speed of (100±10) mm / min. The results are shown in Table 1.

[0107] Table 1:

[0108] As can be seen from Examples 1-3 and Comparative Examples 1-3, and Table 1, the aluminum-plastic composite film prepared using the technical solution of this application exhibits significantly improved resistance to damp heat, heat resistance, and peel strength compared to conventional aluminum-plastic composite films. This is because organic composite microspheres are introduced into the polyurethane, forming more cross-linked structures with the polyurethane and reducing the contact area between unstable, easily hydrolyzed groups and water per unit volume of the polyurethane. This reduces water penetration while improving the stability of the polyurethane. Furthermore, the organic composite microspheres are modified with vegetable oil and combined with nano-titanium dioxide, synergistically improving the heat resistance and water resistance of the polyurethane, and solving the problems of severe agglomeration of nano-titanium dioxide and poor direct grafting effect of vegetable oil in the previous art.

[0109] Based on Examples 1, 4, and 8, and referring to Table 1, it can be seen that the peeling force of the organic composite microspheres is enhanced after modification with vegetable oil. Furthermore, compared to directly grafting vegetable oil onto prepolymers, grafting vegetable oil onto organic composite microspheres improves the performance of polyurethane more effectively. This is because the hydroxyl groups on the vegetable oil can undergo esterification with the carboxyl groups on the organic composite microspheres, thus grafting the vegetable oil onto the organic composite microspheres to form modified organic composite microspheres. Taking castor oil as an example, grafting it onto organic composite microspheres can lower the glass transition temperature of the organic composite microspheres, improve heat resistance, and enhance the toughness and flexibility of the organic composite microspheres, as well as improve the uniformity of crosslinking and the variability of the structure. The surface activity of prepolymers and vegetable oils is not strong, and their compatibility is poor, resulting in unsatisfactory grafting efficiency and effect. Utilizing the good biocompatibility and ease of modification of polymer microspheres, it is convenient to modify the polymer microspheres, serving as a bridge to further improve the performance of polyurethane through the application of vegetable oil.

[0110] As can be seen from Examples 1 and 5 and Table 1, the organic composite microspheres exhibit improved heat resistance and peel strength compared to single polymer microspheres. This is because acrylic acid also possesses good heat resistance, and it can further condense with polyurethane during use, reducing the number of hydrolyzable groups and improving its water resistance. Pentaerythritol triallyl ether also has good heat resistance, and it can further condense with polyurethane, reducing the number of easily hydrolyzed groups in the polyurethane and improving its water resistance. Pentaerythritol triallyl ether also has high viscosity, which can improve the adhesion of polyurethane adhesives. The organic composite microspheres prepared from acrylic acid, pentaerythritol triallyl ether, and polymethyl methacrylate have good compatibility with polyurethane and possess strong hydrophilic properties, capable of absorbing externally penetrating moisture and forming a hydrogel structure, providing support for the polyurethane and thus improving its water resistance. Furthermore, after absorbing a certain amount of water, the organic composite microspheres form a dense stacked structure, which restricts the shear flow of water, increases the viscosity of the overall polyurethane, and forms a hydrophobic layer inside, reducing water penetration. This improves the water resistance of the polyurethane while also increasing its bonding strength. The stacked structure also fills the spatial structure of the polyurethane, thereby improving its mechanical strength and heat resistance.

[0111] As can be seen from Examples 1, 5-7, Comparative Examples 1-2, and Table 1, the nano-titanium dioxide and modified prepolymer used in this application can form a good synergistic effect. The modified polyurethane prepared has significantly improved moisture resistance, heat resistance, and peel strength. The reason is that nanomaterials themselves have strong agglomeration properties. When added as fillers without treatment, the agglomeration effect will affect the performance of the material itself and may have a negative impact on the internal structure of polyurethane. However, after using organic composite microspheres to modify the prepolymer, the organic composite microspheres have a large specific surface area and more active groups on the surface. They can adsorb with nano-titanium dioxide and make it uniformly distributed on the surface of each microsphere, thereby reducing its agglomeration effect. As the organic composite microspheres are more uniformly distributed inside the polyurethane, the thermal stability and water resistance of the polyurethane are synergistically improved.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. An aluminum-plastic composite film, characterized in that, It includes an outer layer, an adhesive layer, an anti-corrosion layer, an aluminum foil layer, an anti-corrosion layer, an adhesive layer, and a heat-sealing layer; The adhesive layer comprises modified polyurethane, which, by weight, comprises the following raw material components: Component A: 2-40 parts polyol, 0.5-2 parts primary auxiliary agent; Component B includes 10-60 parts of modified prepolymer, 2-4 parts of secondary additive, and 1-5 parts of filler; The modified prepolymer in component B is obtained by grafting prepolymer onto polymer microspheres, and the prepolymer is synthesized from isocyanate and polyol. The polymer microspheres are modified organic composite microspheres grafted with plant oil. The modified organic composite microspheres, by weight, include the following raw material components: 22-45 parts polymethyl methacrylate, 8-20 parts acrylic acid, 12-16 parts pentaerythritol triallyl ether, 1-2 parts crosslinking agent, 8-16 parts plant oil, and 0.5-1 parts acid catalyst. The preparation method of the polymer microspheres comprises the following steps: Preparation of organic composite microspheres: Polymethyl methacrylate was dissolved in dichloromethane, then acrylic acid, pentaerythritol triallyl ether and crosslinking agent were added, and the reaction was carried out at 75-85℃ for 40-50 min, and then the temperature was lowered to 50-60℃ and maintained for 50-70 min to obtain organic composite microspheres. Preparation of modified organic composite microspheres: Vegetable oil was added to the organic composite microspheres, an acid catalyst was added, and the reaction was carried out at 70-80℃ for 10-20 min. Then, dichloromethane was removed to obtain modified organic composite microspheres. The filler is nano-titanium dioxide.

2. The aluminum-plastic composite film according to claim 1, characterized in that, The first additive includes one or more of leveling agents, defoamers, antioxidants, and dispersants, and the second additive includes one or more of leveling agents, defoamers, antioxidants, and dispersants.

3. The aluminum-plastic composite film according to claim 1, characterized in that, The modified prepolymer comprises, by weight, the following raw material components: 30-40 parts polyol, 10-20 parts isocyanate, 4-8 parts polymer microspheres, 1-3.6 parts chain extender, and 0.01-0.03 parts catalyst.

4. The aluminum-plastic composite film according to claim 1, characterized in that, The modified prepolymer is prepared according to the following steps: Polyol, isocyanate, catalyst and chain extender are reacted at 75-85℃ for 5-7h to obtain prepolymer; after the prepolymer cools to 20-30℃, polymer microspheres are added and sheared at 2000-3000r / min for 10-30min to obtain modified prepolymer.

5. A method for preparing an aluminum-plastic composite film according to any one of claims 1-4, characterized in that, Prepared using the following steps: An aluminum-plastic composite film is obtained by heat-sealing the outer layer, adhesive layer, anti-corrosion layer, aluminum foil layer, adhesive layer, and heat-sealing layer.