A CPP film for battery packaging aluminum plastic film and a preparation method thereof

Abstract

The application discloses a CPP film for battery packaging aluminum-plastic film and a preparation method thereof, and relates to the technical field of packaging materials. The CPP film comprises a heat-sealing layer, a core layer and a composite layer which are sequentially arranged in layers. The composite layer is made of the following components in parts by weight: 70-90 parts of homopolymer polypropylene, 10-30 parts of propylene-ethylene block copolymer, 5-10 parts of PO polyolefin elastomer, 10-20 parts of modified graphene oxide and 1-3 parts of a crosslinking agent. The finally-prepared CPP film has excellent puncture resistance, heat resistance, barrier property, mechanical strength and composite strength with the surface of an aluminum foil, and is suitable for soft battery aluminum-plastic packaging films.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, specifically to a CPP film for battery encapsulation aluminum-plastic film and its preparation method. Background Technology

[0002] Aluminum-plastic film is the outer packaging material for soft-pack batteries, mainly consisting of a five-layer structure: an outer nylon layer, a nylon adhesive layer, an aluminum foil layer, a CPP adhesive layer, and a CPP layer. The nylon layer, located on the outermost layer of the aluminum-plastic film, is primarily composed of polyamide. Its function is to protect the aluminum-plastic film from scratches, requiring impact resistance and good resistance to damp heat and friction. The aluminum foil layer uses O-state 8021 aluminum foil or 8079 aluminum foil. The aluminum foil prevents moisture from entering the battery and also provides some support. The CPP layer, mainly composed of cast polypropylene, serves as the overall sealing layer of the battery, directly contacting the electrolyte. It requires good electrolyte stability, good adhesion to the battery tabs, and good insulation to prevent internal short circuits. CPP is typically prepared using single-layer or multi-layer co-extrusion processes. Some CPP layers also include additives such as slip agents to ensure good depth of application. The adhesive layer uses polyurethane and polyacrylic acid adhesives, which are required to have good adhesion to adjacent layers to prevent delamination, while also having good resistance to moisture and heat and stability. The CPP layer adhesive also requires good resistance to electrolytes.

[0003] Although the structure of aluminum-plastic film is simple, consisting of only three layers of substrate—nylon, aluminum foil, and CPP—it is not easy to create a material with truly superior performance. Aluminum-plastic film for lithium-ion batteries requires materials with excellent barrier properties, aging resistance, resistance to damp heat, puncture resistance, and resistance to electrolyte corrosion. Unlike aluminum-plastic film used in ordinary food packaging, battery aluminum-plastic film needs to strictly prevent external water and oxygen from entering the battery, thus placing higher demands on the water and oxygen permeability of each component. The lifespan of a soft-pack battery must be at least 8-10 years, therefore the aluminum-plastic film must have aging resistance and remain stable under light, damp heat, and other conditions. Simultaneously, the aluminum-plastic film must have puncture resistance to prevent foreign objects from puncturing the surface during battery encapsulation and use, causing leakage, short circuits, and other problems. The inner CPP layer of the aluminum-plastic film is in direct contact with the electrolyte, requiring it to be resistant to electrolyte corrosion; therefore, the adhesive for the CPP layer and the aluminum foil must also have a certain degree of corrosion resistance. Before battery encapsulation, aluminum-plastic film products undergo stamping. During stamping, the material layers extend and migrate, sliding relative to the stamping die. This involves the stretching and deformation of the substrate and adhesive. The adhesive strength and tensile properties between each layer must be matched to prevent delamination or cracking during deep stamping. CPP, as the inner layer material of the aluminum-plastic film, needs to be in direct contact with the electrolyte, providing insulation and sealing. The electrolyte has strong permeability and can easily corrode and swell the CPP layer, reacting with the adhesive and causing delamination between the CPP and aluminum foil, thus damaging the battery's protective layer and affecting its lifespan. Therefore, the CPP film must possess high barrier properties, as well as good composite strength and heat-sealing performance.

[0004] Chinese patent document CN112918054A discloses a CPP for aluminum-plastic film and its production method. The invention includes an A layer, a B layer, and a C layer. The A layer includes 79.5-89 parts by weight of random copolymer polypropylene, 5-7 parts by weight of organic boron nonionic surfactant, 0.5-1 parts by weight of toughening agent, 1-3 parts by weight of adhesion promoter, 2-5 parts by weight of light shielding agent, 5-10 parts by weight of graphene powder, and 2-5 parts by weight of anti-aging agent.

[0005] Currently, CPP films used as inner layer materials for aluminum-plastic films on the market have problems such as poor barrier properties, low mechanical strength, and poor heat resistance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a CPP film for battery encapsulation aluminum-plastic film and its preparation method. The addition of modified graphene oxide can effectively improve the film's puncture resistance, insulation performance, heat resistance, mechanical strength, and composite strength with aluminum foil surface, thus enabling the prepared CPP film to have a wider range of applications.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A CPP film for battery encapsulation aluminum-plastic film includes a heat-sealing layer, a core layer, and a composite layer stacked sequentially. By weight, the composite layer is made of the following components: 70-90 parts homopolymer polypropylene, 10-30 parts propylene-ethylene block copolymer, 5-10 parts PO polyolefin elastomer, 10-20 parts modified graphene oxide, and 1-3 parts crosslinking agent.

[0009] Preferably, by weight, the heat-sealing layer is made of the following components: 40-80 parts of a propylene-ethylene random copolymer with a melting point of 140-160°C, 10-30 parts of a propylene-ethylene block copolymer with a melting point of 120-135°C, 10-30 parts of a PO polyolefin elastomer with a melting point of 85-100°C, and 2-5 parts of a slip agent; the core layer is made of the following components: 60-90 parts of a propylene-ethylene block copolymer with a melting point of 155-165°C and an ethylene content of 1-7%, and 3-6 parts of a slip agent.

[0010] Preferably, the crosslinking agent is one or more selected from benzoyl peroxide, di-tert-butyl peroxide, and dodecyl peroxide; the homopolymer polypropylene has a melt index of 2.0–5.5 g / 10 min and a density of 0.90–0.92 g / cm³. 3 The propylene-ethylene block copolymer has a melting point of 145-160℃ and an ethylene content of 7-15%; the PO polyolefin elastomer has a melting point of 85-100℃.

[0011] Preferably, the total thickness of the CPP film is 20–100 μm.

[0012] Preferably, the slip agent is one or more of erucamide, stearamide, calcium stearate, zinc stearate, polyethylene wax, and polypropylene wax.

[0013] Preferably, the method for preparing the modified graphene oxide includes the following steps:

[0014] (1) Graphene oxide was dispersed in dimethyl sulfoxide and ultrasonically dispersed. Then 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred to react. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0015] Its structural formula is shown below:

[0016]

[0017] In the formula, Refers to graphene oxide.

[0018] Preferably, in step (1), the mass ratio of graphene oxide to 4-methacryloyloxytriphenyl benzoic anhydride is 10:4.7 to 8.3.

[0019] More preferably, in step (1), the mass ratio of graphene oxide to 4-methacryloyloxytriptamine is 10:6.5.

[0020] Preferably, in step (1), the stirring reaction conditions are 60-75°C for 6-10 hours.

[0021] More preferably, in step (1), the stirring reaction conditions are 70°C for 8 hours.

[0022] (2) Disperse anhydride-modified graphene oxide and aminated cage-type silsesquioxane in dimethyl sulfoxide, then add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, reflux the reaction, filter the product, wash with alcohol and dry to obtain modified graphene oxide.

[0023] Its structural formula is shown below:

[0024]

[0025] Preferably, in step (2), the structure of the aminated cage-type silsesquioxane (POSS-NH2) is as follows:

[0026]

[0027] R: Isobutyl.

[0028] Preferably, in step (2), the mass ratio of anhydride-modified graphene oxide, aminated cage-type silsesquioxane, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 10:2.4-5.6:1-3:1-4.

[0029] More preferably, in step (2), the mass ratio of anhydride-modified graphene oxide, aminated cage-type silsesquioxane, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 10:4:2:2.5.

[0030] Preferably, in step (2), the reflux reaction conditions are reflux reaction at 90-110°C for 4-12 hours.

[0031] More preferably, in step (2), the reflux reaction conditions are reflux reaction at 100°C for 8 hours.

[0032] The present invention also claims a method for preparing the CPP film, wherein the raw materials are mixed according to the formula and melted by three single-screw extruders, and then co-extruded by a batching block connector and a die head and cooled to form a film; the product is subsequently subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1) This invention provides a CPP film for battery encapsulation aluminum-plastic film. The composite layer uses inexpensive homopolymer polypropylene as the main raw material. Homopolymer polypropylene, as a non-crosslinked polymer, generally has low mechanical strength. Therefore, propylene-ethylene block copolymer and elastomer are introduced. The homopolymer polypropylene and propylene-ethylene block copolymer are mixed at high temperature, which disrupts the regular polymer chain segments and reduces the crystallinity of the polymer. This makes the CPP film have a suitable heat sealing temperature. The addition of crosslinking agent and modified graphene oxide can effectively improve the film's puncture resistance, insulation performance, heat resistance, mechanical strength, and composite strength with aluminum foil surface, making it applicable to a wider range of scenarios.

[0035] 2) This invention provides a modified graphene oxide. Firstly, the ring-opening reaction between the hydroxyl groups on the surface of graphene oxide (GO) and 4-methacryloxytriphenylamine anhydride is utilized to graft 4-methacryloxytriphenylamine anhydride onto the GO surface, introducing benzene rings, unsaturated double bonds, and carboxyl groups to obtain anhydride-modified graphene oxide. The introduction of carboxyl groups can improve the composite strength between the film product and the aluminum foil surface, while the introduction of benzene rings can improve the mechanical properties and heat resistance of the CPP film. Simultaneously, the benzene rings can form π-π interactions with the graphene structure, allowing 4-methacryloxytriphenylamine anhydride to effectively embed and adhere between the GO sheets, preventing the re-agglomeration of the peeled GO sheets and improving the dispersibility of GO in the polypropylene matrix. GO dispersed in a monolayer structure provides a more effective filling effect and improves the CPP matrix. The barrier and puncture resistance of P film; in the presence of a crosslinking agent, the methacryloyloxy group on the surface of anhydride-modified graphene oxide can also crosslink with polypropylene, further enhancing the compatibility between graphene oxide and polypropylene materials, and improving the mechanical strength and barrier properties of the prepared CPP film; then, under the action of a carboxyl activator, POSS is grafted onto the GO surface by the amidation reaction between the carboxyl groups on the surface of anhydride-modified graphene oxide and the aminated cage-like silsesquioxane to obtain modified graphene oxide. POSS has both the nanoscale size and cage-like structure of inorganic nanoparticles and the advantages of organic polymers. On the one hand, the organic functional groups on its surface have good compatibility with the polymer matrix. On the other hand, its rigid inorganic silicon-oxygen skeleton can effectively enhance the temperature resistance, oxidation resistance, flame retardancy and mechanical properties of the composite material. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0037] Unless otherwise specified, all chemical reagents and materials in this invention are purchased from the market or synthesized from raw materials purchased from the market.

[0038] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0039] (1) Disperse 10g of graphene oxide in 100mL of dimethyl sulfoxide, disperse by ultrasonication, then add 4.7-8.3g of 4-methacryloyloxytriphenyl oxalic anhydride, stir and react at 60-75℃ for 6-10h, filter, wash and dry the product to obtain anhydride-modified graphene oxide.

[0040] (2) Disperse 10g of anhydride-modified graphene oxide and 2.4-5.6g of amino-modified cage-type silsesquioxane into 100mL of dimethyl sulfoxide, then add 1-3g of dicyclohexylcarbodiimide and 1-4g of 4-dimethylaminopyridine, and reflux at 90-110℃ for 4-12h. Filter, wash with alcohol and dry the product to obtain modified graphene oxide.

[0041] (3) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 20-100μm.

[0042] The composite layer is made of the following components: melt index of 2.0–5.5 g / 10 min and density of 0.90–0.92 g / cm³. 3 The mixture consists of 70-90 parts of homopolymer polypropylene, 10-30 parts of propylene-ethylene block copolymer with a melting point of 145-160℃ and an ethylene content of 7-15%, 5-10 parts of PO polyolefin elastomer with a melting point of 85-100℃, 10-20 parts of modified graphene oxide, and 1-3 parts of crosslinking agent.

[0043] The crosslinking agent is one or more of benzoyl peroxide, di-tert-butyl peroxide, and dodecyl peroxide;

[0044] The heat-sealing layer is made of the following components: 40-80 parts of propylene-ethylene random copolymer with a melting point of 140-160℃, 10-30 parts of propylene-ethylene block copolymer with a melting point of 120-135℃, 10-30 parts of PO polyolefin elastomer with a melting point of 85-100℃, and 2-5 parts of slip agent.

[0045] The core layer is made of the following components: 60-90 parts of propylene-ethylene block copolymer with a melting point of 155-165°C and an ethylene content of 1-7%, and 3-6 parts of slip agent;

[0046] The slip agent is one or more of erucamide, stearamide, calcium stearate, zinc stearate, polyethylene wax, and polypropylene wax.

[0047] The present invention will be further described below through specific embodiments.

[0048] Example 1

[0049] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0050] (1) 10g of graphene oxide was dispersed in 100mL of dimethyl sulfoxide and ultrasonically dispersed. Then 8.3g of 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred at 75℃ for 6h. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0051] (2) 10g of anhydride-modified graphene oxide and 5.6g of amino-modified cage-type silsesquioxane were dispersed in 100mL of dimethyl sulfoxide, and then 3g of dicyclohexylcarbodiimide and 4g of 4-dimethylaminopyridine were added. The mixture was refluxed at 110℃ for 4h. The product was filtered, washed with alcohol, and dried to obtain modified graphene oxide.

[0052] (3) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 60μm.

[0053] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 20g of modified graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0054] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of slip agent.

[0055] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0056] Example 2

[0057] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0058] (1) 10g of graphene oxide was dispersed in 100mL of dimethyl sulfoxide and ultrasonically dispersed. Then 7.1g of 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred at 65℃ for 8h. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0059] (2) 10g of anhydride-modified graphene oxide and 4.5g of amino-modified cage-type silsesquioxane were dispersed in 100mL of dimethyl sulfoxide, and then 2g of dicyclohexylcarbodiimide and 3g of 4-dimethylaminopyridine were added. The mixture was refluxed at 105℃ for 6h. The product was filtered, washed with alcohol and dried to obtain modified graphene oxide.

[0060] (3) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 58μm.

[0061] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 17g of modified graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0062] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of slip agent.

[0063] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0064] Example 3

[0065] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0066] (1) 10g of graphene oxide was dispersed in 100mL of dimethyl sulfoxide and ultrasonically dispersed. Then 5.9g of 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred at 65℃ for 9h. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0067] (2) 10g of anhydride-modified graphene oxide and 3.4g of amino-modified cage-type silsesquioxane were dispersed in 100mL of dimethyl sulfoxide, and then 2g of dicyclohexylcarbodiimide and 2g of 4-dimethylaminopyridine were added. The mixture was refluxed at 95℃ for 8h. The product was filtered, washed with alcohol, and dried to obtain modified graphene oxide.

[0068] (3) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 64μm.

[0069] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 14g of modified graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0070] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of slip agent.

[0071] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0072] Example 4

[0073] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0074] (1) 10g of graphene oxide was dispersed in 100mL of dimethyl sulfoxide and ultrasonically dispersed. Then 4.7g of 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred at 60℃ for 10h. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0075] (2) 10g of anhydride-modified graphene oxide and 2.4g of amino-modified cage-type silsesquioxane were dispersed in 100mL of dimethyl sulfoxide, and then 1g of dicyclohexylcarbodiimide and 1g of 4-dimethylaminopyridine were added. The mixture was refluxed at 90℃ for 12h. The product was filtered, washed with alcohol, and dried to obtain modified graphene oxide.

[0076] (3) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 59μm.

[0077] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 10g of modified graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0078] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of calcium stearate as a slip agent.

[0079] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0080] Comparative Example 1

[0081] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0082] (1) 10g of graphene oxide was dispersed in 100mL of dimethyl sulfoxide and ultrasonically dispersed. Then 8.3g of 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred at 75℃ for 6h. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide.

[0083] (2) The heat-sealing layer, core layer and composite layer raw materials are mixed according to the formula and then melted by three single screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film with a total film thickness of 56μm.

[0084] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 20g of anhydride-modified graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0085] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of calcium stearate as a slip agent.

[0086] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0087] Comparative Example 2

[0088] A method for preparing CPP film for battery encapsulation aluminum-plastic film includes the following steps:

[0089] The raw materials for the heat-sealing layer, core layer, and composite layer are mixed according to the formula and then melted by three single-screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is subsequently subjected to thickness testing, online slitting, winding, and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film, with a total film thickness of 62μm.

[0090] The composite layer is made of the following components: melt flow index of 3.5 g / 10 min and density of 0.91 g / cm³. 3 80g of homopolymer polypropylene, 20g of propylene-ethylene block copolymer with a melting point of 150℃ and an ethylene content of 10%, 7g of PO polyolefin elastomer with a melting point of 90℃, 20g of graphene oxide, and 2g of crosslinking agent benzoyl peroxide.

[0091] The heat-sealing layer is made of the following components: 60g of propylene-ethylene random copolymer with a melting point of 150°C, 20g of propylene-ethylene block copolymer with a melting point of 130°C, 20g of PO polyolefin elastomer with a melting point of 90°C, and 3.5g of calcium stearate as a slip agent.

[0092] The core layer is made of the following components: 75g of propylene-ethylene block copolymer with a melting point of 160°C and an ethylene content of 4%, and 4.5g of calcium stearate as a slip agent.

[0093] The CPP films prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to performance tests. Tensile strength was tested according to GB / T 1040.3-2006 "Determination of Tensile Properties of Plastics - Part 3: Test Conditions for Films and Sheets," and puncture strength was tested using a puncture strength tester. A 100mm × 100mm square sample was placed flat on a stainless steel plate in a constant temperature oven at 120℃ ± 3℃ for 2 minutes. The sample was then removed and cooled to the test environment temperature. Changes in longitudinal and transverse dimensions compared to the initial dimensions were measured, and the thermal shrinkage rate was calculated. The oxygen permeability coefficient of the film was tested using a BTY-B1 film permeability tester, according to GB / T 1038.1-2022 "Test Methods for Gas Permeability of Plastic Products - Films and Sheets - Part 1: Differential Pressure Method," to assess its gas barrier properties. Specific data are shown in Table 1.

[0094] Table 1. Performance test results of CPP film

[0095]

[0096] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A CPP film for battery encapsulation aluminum-plastic film, comprising a heat-sealing layer, a core layer, and a composite layer sequentially stacked, characterized in that, The composite layer is made of the following components in parts by weight: 70-90 parts homopolymer polypropylene, 10-30 parts propylene-ethylene block copolymer, 5-10 parts POE polyolefin elastomer, 10-20 parts modified graphene oxide, and 1-3 parts crosslinking agent. The method for preparing modified graphene oxide includes the following steps: (1) Graphene oxide was dispersed in dimethyl sulfoxide and ultrasonically dispersed. Then 4-methacryloyloxytriphenyl oxalic anhydride was added and stirred to react. The product was filtered, washed and dried to obtain anhydride-modified graphene oxide. (2) Disperse anhydride-modified graphene oxide and amino-modified cage-type silsesquioxane in dimethyl sulfoxide, then add dicyclohexylcarbodiimide and 4-dimethylaminopyridine, reflux the reaction, filter the product, wash with alcohol and dry to obtain modified graphene oxide.

2. The CPP film according to claim 1, characterized in that, By weight, the heat-sealing layer is made of the following components: 40-80 parts of propylene-ethylene random copolymer with a melting point of 140-160℃, 10-30 parts of propylene-ethylene block copolymer with a melting point of 120-135℃, 10-30 parts of POE polyolefin elastomer with a melting point of 85-100℃, and 2-5 parts of slip agent; the core layer is made of the following components: 60-90 parts of propylene-ethylene block copolymer with a melting point of 155-165℃ and an ethylene content of 1-7%, and 3-6 parts of slip agent.

3. The CPP film according to claim 1, characterized in that, The crosslinking agent is one or more selected from benzoyl peroxide, di-tert-butyl peroxide, and dodecyl peroxide; the homopolymer polypropylene has a melt index of 2.0~5.5 g / 10 min and a density of 0.90~0.92 g / cm³. 3 The propylene-ethylene block copolymer has a melting point of 145~160℃ and an ethylene content of 7~15%; the POE polyolefin elastomer has a melting point of 85~100℃.

4. The CPP film according to claim 1, characterized in that, The total thickness of the CPP film is 20~100μm.

5. The CPP film according to claim 1, characterized in that, In step (1), the mass ratio of graphene oxide to 4-methacryloyloxytriphenyl oxalic anhydride is 10:4.7~8.

3.

6. The CPP film according to claim 1, characterized in that, In step (1), the stirring reaction conditions are 60~75℃ for 6~10h.

7. The CPP film according to claim 1, characterized in that, In step (2), the mass ratio of anhydride-modified graphene oxide, aminated cage-type silsesquioxane, dicyclohexylcarbodiimide, and 4-dimethylaminopyridine is 10:2.4~5.6:1~3:1~4.

8. The CPP film according to claim 1, characterized in that, In step (2), the reflux reaction conditions are reflux reaction at 90~110℃ for 4~12h.

9. The method for preparing the CPP film according to any one of claims 1 to 8, characterized in that, The raw materials are mixed according to the formula and then melted by three single-screw extruders. The mixture is then co-extruded by the batching block connector and die head and cooled to form a film. The product is then subjected to thickness detection, online slitting, winding and packaging to obtain the CPP film for battery encapsulation aluminum-plastic film.

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