Heat sealing layer and application thereof in preparation of CPP film and aluminum plastic film

Abstract

The invention discloses a heat sealing layer and application thereof in preparation of a CPP film and an aluminum plastic film, first raw materials for forming the heat sealing layer comprise 58-82% of polypropylene random copolymer and 10-30% of homo-polypropylene, the polypropylene random copolymer is a propylene, ethylene and butylene ternary random copolymer, the density of the polypropylene random copolymer is 0.88-0.93 g / cm < 3 >, the melt index is 4-12 g / 10 min, and the melting point is 120-140 DEG C; the density of the homo-polypropylene is 0.88-0.93 g / cm < 3 >, the melt index is 6-14 g / 10 min, and the melting point is 160-170 DEG C. The heat-sealing layer is used for preparing the CPP film, and the CPP film has good low-temperature heat-sealing performance, high heat-sealing strength, good electrolyte resistance, stable friction before and after high-temperature curing, high peel strength and uniform whitening effect after one-sealing and two-sealing.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery packaging materials, and particularly relates to a heat-sealing layer and its application in the preparation of CPP film and aluminum-plastic film. Background Technology

[0002] Based on their packaging methods, lithium-ion batteries are generally classified into three categories: cylindrical lithium batteries, prismatic lithium batteries, and pouch lithium batteries encapsulated with an aluminum-plastic composite film. Cylindrical or prismatic lithium batteries are typically encapsulated using stainless steel or aluminum alloy materials, hence they are also called hard-shell lithium batteries. Pouch lithium batteries generally use an aluminum-plastic composite film as the encapsulation material. They are small in size, lightweight, and offer flexibility in shape and size, allowing for diverse designs to meet various complex battery shapes and higher energy density requirements, adapting to the trend of thinner and smaller batteries. Simultaneously, pouch batteries possess excellent ductility. When air bulges inside the pouch cell, the excellent ductility of the aluminum-plastic film provides sufficient buffer space for the gas. Before reaching the battery's explosion threshold, the aluminum-plastic film will tear, preventing a potential explosion and ensuring safety. Therefore, using an aluminum-plastic composite film as the outer shell material will be the future development direction for various lithium-ion batteries.

[0003] Dry-process lithium battery aluminum-plastic film packaging materials mainly include PET, nylon, aluminum foil, CPP, and an adhesive layer. The structure from the outside in is generally PET / PA / AL / CPP. PET is typically 12µm thick, primarily serving to protect the nylon layer from electrolyte dripping and corroding during processing. Nylon is typically 25µm thick, ensuring the mechanical strength of the battery packaging, providing scratch resistance, puncture resistance, impact resistance, and preventing external damage to the battery. Aluminum foil is typically 40-50µm thick, primarily functioning as a barrier, light shielding, and ensuring molding flexibility. CPP is typically 40-80µm thick, primarily preventing electrolyte corrosion of the aluminum foil and performing the crucial heat-sealing function. The layers are bonded together with a 2-4µm adhesive layer. As a heat-sealing layer material, CPP film has extremely high requirements for sealing temperature, heat-sealing strength, bonding strength with aluminum foil, and electrolyte resistance, making it one of the major technical challenges in the aluminum-plastic film packaging industry. Among them, the heat-sealing layer is an important factor affecting the low-temperature heat-sealing performance, heat-sealing strength and electrolyte resistance of CPP film. However, the existing heat-sealing layer is difficult to make CPP film have good low-temperature heat-sealing performance, heat-sealing strength, electrolyte resistance and uniform whitening effect after one and two sealing. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the heat-sealing layer provided by this invention is used to prepare CPP films. The CPP films have good low-temperature heat-sealing performance, high heat-sealing strength, good electrolyte resistance, frictional stability before and after high-temperature curing, high peel strength, and uniform whitening effect after one and two sealing processes.

[0005] The purpose of this invention is to provide a heat-sealing layer, wherein the first raw material forming the heat-sealing layer, by weight percentage, comprises: 58-82% random copolymer polypropylene and 10-30% first homopolymer polypropylene, wherein the random copolymer polypropylene is a terpolymer random copolymer of propylene, ethylene, and butene, and the density of the random copolymer polypropylene is 0.88-0.93 g / cm³. 3 The melt index is 4~12 g / 10 min, and the melting point is 120~140℃; the density of the first homopolymer polypropylene is 0.88~0.93 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 160~170℃.

[0006] In some embodiments of the present invention, the first raw material further includes 0.5-6% silica opening agent and 0.5-6% erucamide type slip agent.

[0007] Another object of the present invention is to provide a CPP film comprising a heat-sealing layer, a core layer and a composite layer arranged in sequence.

[0008] In some embodiments of the present invention, the second raw material forming the core layer comprises, by weight percentage, 51-88% block copolymer polypropylene and 2-15% high-density polyethylene, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88-0.92 g / cm³. 3 The melt index is 1~6 g / 10 min, and the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 128~140℃.

[0009] In some embodiments of the present invention, the second raw material further includes 10-30% polyolefin elastomer, wherein the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85-0.90 g / cm³. 3 The melt index is 1~6g / 10min, and the melting point is 60~100℃.

[0010] In some embodiments of the present invention, the second raw material further includes 0.2-4% of an erucamide-type slip agent.

[0011] In some embodiments of the present invention, the third raw material forming the composite layer, by mass percentage, comprises 95-100% second homopolymer polypropylene and 0-5% silica opening agent, wherein the density of the second homopolymer polypropylene is 0.88-0.93 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 160~170℃.

[0012] In some embodiments of the present invention, in the CPP film, the thickness percentages of the heat-sealing layer, the core layer, and the composite layer are 5-25%: 50-90%: 5-25%. Specifically, the thickness percentages of the heat-sealing layer, the core layer, and the composite layer include, but are not limited to, 5%:90%:5%, 10%:80%:10%, 15%:70%:15%, 20%:60%:20%, and 25%:50%:25%.

[0013] In some embodiments of the present invention, the thickness of the CPP film is 30~100um.

[0014] Another objective of this invention is to provide a method for preparing the CPP film, which uses a multilayer co-extrusion casting technique to form a heat-sealing layer, a core layer, and a composite layer that are sequentially stacked.

[0015] Another object of the present invention is to provide an aluminum-plastic film, including the CPP film.

[0016] In some embodiments of the present invention, the aluminum-plastic film further includes a PET layer, a nylon layer and an aluminum foil layer, with the nylon layer, the aluminum foil layer and the CPP film sequentially stacked on the PET layer.

[0017] In some embodiments of the present invention, the thickness of the PET layer is 10~14 μm.

[0018] In some embodiments of the present invention, the thickness of the nylon layer is 20~30 μm.

[0019] In some embodiments of the present invention, the thickness of the aluminum foil layer is 40~50um.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The heat-sealing layer CPP film of the present invention has a low initial sealing temperature, high heat-sealing strength, and can be heat-sealed quickly, thereby improving the product packaging efficiency and making it suitable for applications such as 3C electronic products or small batteries.

[0022] (2) The CPP film of the present invention has a low heat sealing temperature and high heat sealing strength; it is stable in friction before and after high temperature curing; the first and second sealing sols of the CPP film after high temperature composite are uniformly white; it maintains high peel strength with aluminum foil before and after immersion in electrolyte; after the product is filled with electrolyte and left for a long time, it has good electrolyte resistance and excellent crystal point level. Attached Figure Description

[0023] Figure 1 The whitening effect of the CPP film at the sealing point in Example 1.

[0024] Figure 2 The whitening effect of the CPP film in Example 1 during the second sealing process.

[0025] Figure 3 The whitening effect of the CPP film at the sealing point is shown in Comparative Example 1.

[0026] Figure 4 The whitening effect of the CPP film during the second sealing process is shown in Comparative Example 1. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0028] All raw materials used in this invention are commercially available.

[0029] Example 1

[0030] This embodiment provides a CPP membrane, and the specific process is as follows:

[0031] The raw materials forming the heat-sealing layer, by weight percentage, are: 82% random copolymer polypropylene, 10% homopolymer polypropylene, 4% silica opening agent, and 4% erucamide-type slip agent. The random copolymer polypropylene is a terpolymer random copolymer of propylene, ethylene, and butene, and its density is 0.88 g / cm³. 3 The melt index is 4 g / 10min, and the melting point is 140 ℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 170 ℃;

[0032] The raw materials forming the core layer are: 63% block copolymer polypropylene, 10% high-density polyethylene, 25% polyolefin elastomer, and 2% erucamide-type slip agent. The block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and its density is 0.88 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 150 °C; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 128 ℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.90 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 60 °C.

[0033] The raw materials forming the composite layer are: 95% homopolymer polypropylene and 5% silica opening agent, wherein the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index is 14 g / 10min, and the melting point is 160 ℃;

[0034] According to the mass percentage, the raw materials for the heat-sealing layer, core layer, and composite layer are melted separately at high temperature in the screw according to the required proportions. The melted materials are then fed into three extruders corresponding to the three-layer co-extrusion casting machine. The thickness percentages of the three layers are set as 15%:70%:15%. The extrusion temperature of the die head is 180~270℃. Specifically, the extruder temperature for forming the heat-sealing layer is 180℃ and the extrusion rate is 90 kg / h. The extruder temperature for forming the core layer is 180℃ and the extrusion rate is 400 kg / h. The extruder temperature for forming the composite layer is 180℃ and the extrusion rate is 90 kg / h. The film is cooled and shaped on the smooth roller at a temperature of 20~60℃. After stretching by each guide roller, tempering, corona treatment, thickness detection, online defect monitoring, trimming, and winding, the production line speed is 50m / min and the winding tension is 5 kg, resulting in a 40μm CPP film.

[0035] Example 2

[0036] This embodiment provides a CPP membrane, and the specific process is as follows:

[0037] The difference from Example 1 lies in the mass percentage of the raw materials forming the heat-sealing layer and the percentage of the set thickness of the three layers; otherwise, they are the same as in Example 1. By mass percentage, the raw materials forming the heat-sealing layer in this example are: 58% random copolymer polypropylene, 30% homopolymer polypropylene, 6% silica opening agent, and 6% erucamide-type slip agent. The random copolymer polypropylene is a terpolymer of propylene, ethylene, and butene, and its density is 0.88 g / cm³. 3 The melt index is 4 g / 10 min, and the melting point is 140℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index was 6 g / 10 min and the melting point was 170℃; the thickness percentage of the three layers was set to 5%:90%:5%; a 50 μm CPP film was obtained.

[0038] Example 3

[0039] This embodiment provides a CPP membrane, and the specific process is as follows:

[0040] The difference from Example 1 lies in the mass percentage of the raw materials forming the heat-sealing layer and the set thickness percentage of the three layers; otherwise, they are the same as in Example 1. By mass percentage, the raw materials forming the heat-sealing layer in this example are: 74% random copolymer polypropylene, 25% homopolymer polypropylene, 0.5% silica opening agent, and 0.5% erucamide-type slip agent. The random copolymer polypropylene is a terpolymer random copolymer of propylene, ethylene, and butene, and its density is 0.88 g / cm³. 3 The melt index is 4 g / 10min, and the melting point is 140℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index was 6 g / 10 min and the melting point was 170℃; the thickness percentage of the three layers was set to 25%:50%:25%; a CPP film with a thickness of 45 μm was obtained.

[0041] Example 4

[0042] This embodiment provides a CPP membrane, and the specific process is as follows:

[0043] The difference from Example 1 lies in the raw materials used to form the heat-sealing layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the heat-sealing layer in this example are: 72% random copolymer polypropylene and 28% homopolymer polypropylene. The random copolymer polypropylene is a terpolymer random copolymer of propylene, ethylene, and butene, and its density is 0.88 g / cm³. 3 The melt index is 4 g / 10min, and the melting point is 140℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 It has a melt index of 6 g / 10min and a melting point of 170℃.

[0044] Example 5

[0045] This embodiment provides a CPP membrane, and the specific process is as follows:

[0046] The difference from Example 1 lies in the raw materials used to form the core layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the core layer in this example are: 51% block copolymer polypropylene, 15% high-density polyethylene, 30% polyolefin elastomer, and 4% erucamide-type slip agent. The block copolymer polypropylene is an ethylene-propylene copolymer, and its density is 0.9 g / cm³. 3 The melt index is 3 g / 10min, and the melting point is 160℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 128 ℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.90 g / cm³. 3 It has a melt index of 6 g / 10min and a melting point of 60 ℃.

[0047] Example 6

[0048] This embodiment provides a CPP membrane, and the specific process is as follows:

[0049] The difference from Example 1 lies in the raw materials used to form the core layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the core layer in this example are: 87.8% block copolymer polypropylene, 2% high-density polyethylene, 10% polyolefin elastomer, and 0.2% erucamide-type slip agent. The block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and its density is 0.88 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 150 °C; the density of the high-density polyethylene is 0.957 g / cm³. 3 The melt index is 9 g / 10min, and the melting point is 130 °C; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.90 g / cm³. 3 It has a melt index of 6 g / 10min and a melting point of 60 ℃.

[0050] Example 7

[0051] This embodiment provides a CPP membrane, and the specific process is as follows:

[0052] The difference from Example 1 lies in the raw materials used to form the core layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the core layer in this example are: 63% block copolymer polypropylene, 10% high-density polyethylene, 25% polyolefin elastomer, and 2% erucamide-type slip agent. The block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 150 °C; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 128 °C; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 g / cm³. 3 The melt index is 5g / 10min, and the melting point is 95℃.

[0053] Example 8

[0054] This embodiment provides a CPP membrane, and the specific process is as follows:

[0055] The difference from Example 1 lies in the raw materials used to form the core layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the core layer in this example are: 65% block copolymer polypropylene, 10% high-density polyethylene, and 25% polyolefin elastomer. The block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 150 °C; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10min, and the melting point is 128 ℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.90 g / cm³. 3 It has a melt index of 6 g / 10min and a melting point of 60 ℃.

[0056] Example 9

[0057] This embodiment provides a CPP membrane, and the specific process is as follows:

[0058] The difference from Example 1 lies in the raw materials used to form the composite layer; otherwise, they are the same as in Example 1. By mass percentage, the raw materials used to form the composite layer in this example are: 95% homopolymer polypropylene and 5% silica opening agent, wherein the density of the homopolymer polypropylene is 0.89 g / cm³. 3 It has a melt index of 6 g / 10min and a melting point of 166℃.

[0059] Example 10

[0060] This embodiment provides a CPP membrane, and the specific process is as follows:

[0061] The difference from Example 1 lies in the raw material used to form the composite layer; otherwise, they are the same as in Example 1. By mass percentage, the raw material used to form the composite layer in this example is 100% homopolymer polypropylene, wherein the density of the homopolymer polypropylene is 0.88 g / cm³. 3 The melt index is 14 g / 10min and the melting point is 160 ℃.

[0062] Comparative Example 1

[0063] This comparative example provides a CPP membrane, and the specific process is as follows:

[0064] The difference from Example 1 lies in the raw material used to form the heat-sealing layer, random copolymer polypropylene. Otherwise, it is the same as Example 1. In this comparative example, the raw material for forming the heat-sealing layer, random copolymer polypropylene, is an ethylene-propylene copolymer, and the density of the random copolymer polypropylene is 0.9 g / cm³. 3 The melt index is 13 g / 10min and the melting point is 125 ℃.

[0065] Comparative Example 2

[0066] This comparative example provides a CPP membrane, and the specific process is as follows:

[0067] The difference from Example 1 is that the homopolymer polypropylene used to form the heat-sealing layer is different; otherwise, it is the same as Example 1. The density of the homopolymer polypropylene used to form the heat-sealing layer in this comparative example is 0.89 g / cm³. 3 The melt index is 12g / 10min, and the melting point is 155℃.

[0068] Performance testing:

[0069] In Tables 1 and 2, "before lamination" refers to CPP film, and "after lamination" refers to aluminum-plastic film, which is an aluminum-plastic film obtained by sequentially stacking a PET layer, a nylon layer, an aluminum foil layer, and the CPP film of Examples 1-10 or Comparative Examples 1-2, respectively. The thickness of the PET layer is 12 μm, the thickness of the nylon layer is 25 μm, and the thickness of the aluminum foil layer is 45 μm.

[0070] Heat sealing strength at various heat sealing temperatures: QB / T 2358; One-sealing refers to the direct sealing at the joint after lamination, without the need for electrolyte coating, while two-sealing involves coating the joint with electrolyte before heat sealing.

[0071] Electrolyte resistance: The composite aluminum-plastic film was cut into strips with a width of 15 mm and a length of 100 mm. These strips were then immersed in a container containing electrolyte and 1000~1500 ppm of water and left to stand at 85°C. The peel strength between the CPP film and aluminum foil was then tested at different time periods (initial value, 8h, 1 day, 2 days, 5 days, 7 days, 14 days, 30 days, and 60 days).

[0072] Friction coefficient: Refer to GB / T 10006; friction coefficient before compounding and friction coefficient after compounding and curing at 60℃ for 5 days.

[0073] Table 1. Performance test results of CPP film or aluminum-plastic film.

[0074]

[0075] As shown in Table 1, the raw materials of the core layer and composite layer of the present invention have little effect on the low-temperature heat-sealing performance and heat-sealing strength of CPP film or aluminum-plastic film. The silica opening agent and erucamide-type slip agent of the heat-sealing layer also have little effect on the low-temperature heat-sealing performance and heat-sealing strength of CPP film or aluminum-plastic film.

[0076] Table 2. Performance test results of CPP film or aluminum-plastic film.

[0077]

[0078] As shown in Tables 1 and 2, the random copolymer polypropylene and homopolymer polypropylene used in the heat-sealing layer of the present invention can effectively improve the low-temperature heat-sealing performance, heat-sealing strength, electrolyte resistance, and uniform whitening effect of the first and second seals of CPP film or aluminum-plastic film; while the electrolyte resistance and the first and second seal heat-sealing strength of the random copolymer polypropylene used in the heat-sealing layer of Comparative Example 1 are both reduced; and the heat-sealing strength of the homopolymer polypropylene used in the heat-sealing layer of Comparative Example 2 is reduced in both the heat-sealing strength before and after the composite heat-sealing.

[0079] Depend on Figure 1 and Figure 2 It can be seen that after peeling off both surfaces of the CPP film obtained in Example 1, there is still a thin film protecting the aluminum foil on the surface, and there is no aluminum leakage. It can be determined that the electrolyte did not penetrate the CPP film into the aluminum foil layer and thus corrode the aluminum foil. Whether it is the first or second seal, it is uniformly white. The CPP films obtained in Examples 2 to 10 have similar effects to those in Example 1. However, after peeling off both surfaces of the CPP film obtained in Comparative Example 1, the film at the seal point cracked, and the sealing effect was poor.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this application specification, they can still modify or make equivalent substitutions to the specific implementation of the present invention, but these modifications or changes do not depart from the protection scope of the pending claims of the present invention.

Claims

1. A heat-sealing layer, characterized in that, The first raw material forming the heat-sealing layer, by weight percentage, comprises: 58-82% random copolymer polypropylene and 10-30% first homopolymer polypropylene, wherein the random copolymer polypropylene is a terpolymer random copolymer of propylene, ethylene, and butene, and the density of the random copolymer polypropylene is 0.88-0.93 g / cm³. 3 The melt index is 4~12 g / 10 min, and the melting point is 120~140℃; the density of the first homopolymer polypropylene is 0.88~0.93 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 160~170℃.

2. The heat-sealing layer as described in claim 1, characterized in that, The first raw material also includes 0.5-6% silica opening agent and 0.5-6% erucamide type slip agent.

3. A CPP film, said CPP film comprising a heat-sealing layer, a core layer, and a composite layer sequentially stacked, characterized in that, The heat-sealing layer is the heat-sealing layer according to any one of claims 1 to 2.

4. The CPP membrane as described in claim 3, wherein, by mass percentage, the second raw material of the core layer comprises 51-88% block copolymer polypropylene and 2-15% high-density polyethylene, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88-0.92 g / cm³. 3 The melt index is 1~6 g / 10 min, and the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 128~140℃.

5. The CPP membrane according to claim 4, characterized in that, The second raw material also includes 10-30% polyolefin elastomer, wherein the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85-0.90 g / cm³. 3 The melt index is 1~6g / 10min, and the melting point is 60~100℃.

6. The CPP membrane according to claim 4, characterized in that, The second raw material also includes 0.2-4% of erucamide-type slip agent.

7. The CPP membrane as described in claim 3, characterized in that, By mass percentage, the third raw material of the composite layer comprises 95-100% second homopolymer polypropylene and 0-5% silica opening agent, wherein the density of the second homopolymer polypropylene is 0.88-0.93 g / cm³. 3 The melt index is 6~14g / 10min, and the melting point is 160~170℃.

8. The CPP membrane according to any one of claims 3 to 7, characterized in that, In the CPP film, the thickness percentages of the heat-sealing layer, the core layer, and the composite layer are 5~25%: 50~90%: 5~25%.

9. A method for preparing the CPP membrane according to claims 3-7, characterized in that, The heat-sealing layer, core layer and composite layer are formed by sequentially stacking them using multi-layer co-extrusion casting technology.

10. An aluminum-plastic film, comprising a CPP film, characterized in that, The CPP membrane is the CPP membrane according to any one of claims 3 to 8.

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