A polypropylene film for an al-plastic film, an al-plastic film, and a battery

Abstract

The application discloses a polypropylene film for an aluminum-plastic film, the aluminum-plastic film and a battery, and relates to the technical field of battery packaging materials. The polypropylene film comprises a heat-sealing layer, a core layer and a corona layer which are sequentially arranged in layers; wherein the material forming the core layer comprises first polypropylene and first polyolefin elastomer, the mass content of the rubber phase in the first polypropylene is 15% to 25%, and the melting point of the first polyolefin elastomer is 100 to 160 DEG C. The aluminum-plastic film formed by the polypropylene film has excellent punch deep forming performance, high-temperature resistance and electrolyte resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery packaging materials, in particular to a polypropylene film for an aluminum-plastic film, the aluminum-plastic film and a battery. BACKGROUND

[0002] The battery cell is mainly soft-packed by the aluminum-plastic film, and the electrolyte is injected to form a soft-packaged battery. By improving the deep drawing performance of the aluminum-plastic film, the energy density of the battery can be increased. The aluminum-plastic film includes an inner layer, an aluminum foil layer and an outer layer which are sequentially stacked. In order to make the aluminum-plastic film have excellent deep drawing performance, the layer structure is mainly adjusted at present, for example, the thickness of the aluminum foil layer and the thickness of the outer layer are increased. The improvement degree of these methods for the deep drawing performance is limited. At present, the influence of the physical and chemical properties of the inner layer (polypropylene casting film) itself on the deep drawing performance is less studied. In addition, the inner layer is directly in contact with the battery cell and the electrolyte, and the high temperature resistance and the electrolyte resistance of the inner layer will directly affect the safety and packaging of the battery. However, the improvement degree is limited by adding a passivation layer in the aluminum-plastic film to make the aluminum-plastic film have good high temperature resistance and electrolyte resistance. Therefore, how to provide a polypropylene film which can improve the deep drawing performance and has good high temperature resistance and electrolyte resistance is a technical problem to be solved in the field. SUMMARY

[0003] The main purpose of the present application is to provide a polypropylene film for an aluminum-plastic film, an aluminum-plastic film and a battery, so as to solve the problem that there is no polypropylene film for improving the deep drawing performance and having good high temperature resistance and electrolyte resistance in the prior art.

[0004] In order to achieve the above-mentioned purpose, according to the first aspect of the present application, a polypropylene film for an aluminum-plastic film is provided, the polypropylene film includes a heat sealing layer, a core layer and a corona layer which are sequentially stacked.

[0005] The material forming the core layer includes a first polypropylene and a first polyolefin elastomer, the mass content of the rubber phase in the first polypropylene is 15% to 25%, and the melting point of the first polyolefin elastomer is 100 to 160℃.

[0006] Further, the thickness of the heat sealing layer accounts for 5% to 20% of the thickness of the polypropylene film, the thickness of the core layer accounts for 60% to 90% of the thickness of the polypropylene film, and the thickness of the corona layer accounts for 5% to 20% of the thickness of the polypropylene film.

[0007] Further, the mass content of ethylene in the rubber phase of the first polypropylene is 20% to 40%.

[0008] Further, the mass content of the first polyolefin elastomer in the material forming the core layer is ≤30%.

[0009] Preferably, the mass content of the first polypropylene in the material forming the core layer is 70-95%, and the mass content of the first polyolefin elastomer is 5-30%.

[0010] Further, the material forming the heat-seal layer comprises a second polypropylene and a second polyolefin elastomer;

[0011] Preferably, the mass content of the second polypropylene in the material forming the heat-seal layer is 90-97%, and the mass content of the second polyolefin elastomer is 3-10%.

[0012] Preferably, the melting point of the second polyolefin elastomer is lower than that of the first polyolefin elastomer.

[0013] Further, the melting point of the second polyolefin elastomer is 50-80℃.

[0014] Further, the first polyolefin elastomer and the second polyolefin elastomer are each independently selected from at least one of ethylene-α-olefin elastomer and propylene-α-olefin elastomer.

[0015] Preferably, the first polyolefin elastomer is a copolymer of propylene monomer and ethylene monomer, or the first polyolefin elastomer is a copolymer of propylene monomer and 1-butene monomer.

[0016] Preferably, the second polyolefin elastomer is a copolymer of ethylene monomer and 1-butene monomer, or the first polyolefin elastomer is a copolymer of ethylene monomer and 1-octene monomer.

[0017] Preferably, the weight average molecular weight of the first polyolefin elastomer is 150-250 thousand, and the weight average molecular weight of the second polyolefin elastomer is 120-200 thousand.

[0018] Further, the first polypropylene is a block copolymerized polypropylene, and the second polypropylene is a binary random copolymerized polypropylene or a ternary random copolymerized polypropylene.

[0019] Preferably, the first polypropylene is a block copolymer of propylene monomer and ethylene monomer; the second polypropylene is a random copolymer of propylene monomer and ethylene monomer; or the second polypropylene is a random copolymer of propylene monomer and butene monomer; or the second polypropylene is a random copolymer of ethylene monomer, propylene monomer and butene monomer.

[0020] Preferably, the weight average molecular weight of the first polypropylene is 200-500 thousand, and the weight average molecular weight of the second polypropylene is 200-400 thousand.

[0021] Further, the material forming the corona layer comprises a third polypropylene, and the third polypropylene is a binary random copolymerized polypropylene.

[0022] Preferably, the third polypropylene is a binary random copolymer polymerized from propylene monomers and ethylene monomers; or, the third polypropylene is a binary random copolymer polymerized from propylene monomers and butylene monomers.

[0023] Preferably, the third polypropylene has a weight average molecular weight of 200-400 thousand.

[0024] In a second aspect, the present application provides an aluminum-plastic film, which comprises an inner layer, an aluminum foil layer and an outer layer arranged in sequence, wherein the inner layer is the polypropylene film for aluminum-plastic film provided in the first aspect, the corona layer of the polypropylene film is attached to one surface of the aluminum foil layer, and the other surface of the aluminum foil layer is attached to the outer layer.

[0025] In a third aspect, the present application provides a battery, which comprises a battery cell and the aluminum-plastic film provided in the second aspect, and the aluminum-plastic film is used for packaging the battery cell.

[0026] By limiting the composition of the polypropylene film and the physical parameters such as the rubber phase content of the first polypropylene and the melting point of the first polyolefin elastomer, the impact strength and toughness of the polypropylene film can be improved, the yield elongation can be increased, the generation of silver streaks and micro-cracks during the cold stamping forming process of the polypropylene film in the preparation of the aluminum-plastic film can be reduced, the aluminum foil layer can be effectively protected from being excessively stretched to generate pinholes during the stamping process, the deep stamping performance of the aluminum-plastic film formed by the polypropylene film is improved, in addition, the ability of the polypropylene film to resist penetration of polar solvents in electrolyte can be enhanced, the aluminum-plastic film prepared therefrom has good electrolyte resistance, the polypropylene film has good thermal stability, the bonding strength between the layers of the aluminum-plastic film is ensured, the aluminum-plastic film prepared therefrom has good high-temperature resistance, and the aluminum-plastic film prepared from the polypropylene film applied in the battery helps to improve the energy density and safety performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a structural schematic diagram of the polypropylene film for aluminum-plastic film in an embodiment of the present application;

[0028] Figure 2 FIG. 2 is a structural schematic diagram of the aluminum-plastic film in an embodiment of the present application.

[0029] REFERENCE SIGNS:

[0030] 1-polypropylene film; 11-core layer; 12-corona layer; 13-heat-seal layer; 2-aluminum foil layer; 3-outer layer. DETAILED DESCRIPTION

[0031] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. If specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturers are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted.

[0032] As described in the background of the present application, there is no polypropylene film in the prior art that can improve the deep draw forming performance and has good electrolyte resistance. In order to solve the above problems, as shown in the present application, Figure 1 The first aspect of the present application provides a polypropylene film 1 for an aluminum-plastic film, the polypropylene film 1 comprising a heat-sealing layer 13, a core layer 11 and a corona layer 12 arranged in sequence, the material forming the core layer 11 comprising a first polypropylene and a first polyolefin elastomer, the mass content of the rubber phase in the first polypropylene being 15% to 25%, and the melting point of the first polyolefin elastomer being 100 to 160°C.

[0033] In the specific implementation of the present application, the above-mentioned polypropylene film 1 for an aluminum-plastic film can be used as the inner layer of the aluminum-plastic film, at this time, the heat-sealing layer 13 plays a packaging role, the core layer 11 plays a whole supporting role, and the corona layer 12 is attached to the aluminum foil layer 2 to play a bonding role.

[0034] In the polypropylene film 1 for an aluminum-plastic film of the present application, the core layer 11 is an important component of the aluminum-plastic film, and the performance of the core layer 11 directly affects the performance and quality of the aluminum-plastic film. The material forming the core layer 11 comprises a first polypropylene and a first polyolefin elastomer, that is, the core layer 11 is obtained by film-forming of the slurry formed by the first polypropylene and the first polyolefin elastomer.

[0035] Specifically, the first polypropylene is a thermoplastic plastic, which comprises a polypropylene matrix polymerized by propylene monomers. The first polypropylene also comprises a rubber phase, which can be a copolymer (such as ethylene-propylene rubber) polymerized by ethylene monomers and propylene monomers. The rubber phase can form a dispersed phase in the polypropylene matrix, and the content of the rubber phase directly affects the physical properties of the first polypropylene, such as elasticity, impact resistance and the like, thereby improving the overall performance of the material.

[0036] The mass content of the rubber phase in the first polypropylene is 15% to 25%, for example, 15%, 18%, 20%, 22%, 25% or a range formed by any two of them. By limiting the content of the rubber phase in the first polypropylene, the polypropylene film 1 has better toughness and impact resistance, and the deep draw forming performance of the aluminum-plastic film formed by the polypropylene film 1 can be improved.

[0037] It should be noted that the first polypropylene sample can be analyzed by infrared spectroscopy (FTIR) to identify the characteristic absorption peaks of the rubber phase therein, and by quantitatively analyzing the intensities of these peaks, the content of the rubber phase can be calculated.

[0038] The first polyolefin elastomer can be a polymer copolymerized from propylene and an α-olefin such as ethylene, 1-butene, 1-hexene, etc. This kind of polymer has good elasticity, heat resistance and chemical resistance. The addition of the first polyolefin elastomer in the polypropylene film 1 can improve its performance, such as improving the high temperature resistance, chemical resistance, etc., so that the polypropylene film 1 has good high temperature resistance and electrolyte resistance.

[0039] The melting point of the polyolefin elastomer will directly affect its thermal stability. The polyolefin elastomer with a higher melting point usually has better thermal stability and can maintain its performance at a higher temperature. In addition, the regularity of the molecular chain and the crystallinity and molecular weight will affect the melting point. The higher the regularity of the molecular chain, the greater the crystallinity, the higher the melting point; the greater the molecular weight, the stronger the interaction force between the molecular chains, the higher the melting point. The melting point of the first polyolefin elastomer is 100-160°C, such as 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or a range formed by any two of them. By limiting the melting point of the first polyolefin elastomer to 100-160°C, the thermal stability of the polypropylene film 1 can be improved, and the bonding strength between the polypropylene film 1 and the aluminum foil layer 2 can be ensured in a high temperature environment, so that the aluminum-plastic film has more excellent high temperature resistance. When the melting point of the first polyolefin elastomer is 100-160°C, it indicates that the first polyolefin elastomer of the present application has high regularity of the molecular chain, high crystallinity, large molecular weight and strong interaction force between the molecular chains, which can further improve the high temperature resistance and electrolyte resistance of the polypropylene film 1 formed therefrom.

[0040] It should be noted that the melting point of the first polyolefin elastomer can be measured by differential scanning calorimetry (DSC). The heat change of the sample during heating or cooling can be measured to obtain the melting point and other thermal performance parameters of the sample. Specifically, the first polyolefin elastomer sample to be tested is ground into fine powder to ensure that the contact area between the sample and the heat is large enough. The weighed sample is placed in a crucible to ensure uniform distribution of the sample. The crucible containing the sample is placed in a differential scanning calorimeter, and appropriate heating or cooling rate, temperature range and other parameters are set. The heat change between the sample and the reference material is recorded in real time according to the set experimental conditions. On the differential scanning calorimetry curve formed, the melting point usually shows a clear endothermic peak, and the melting point of the first polyolefin can be obtained by analyzing the position of the endothermic peak.

[0041] The polypropylene film 1 for the aluminum-plastic film of the present application can improve the impact strength and toughness of the polypropylene film 1, increase the yield elongation, reduce the generation of silver streaks and micro-cracks during the cold stamping forming process when preparing the aluminum-plastic film, effectively protect the aluminum foil layer 2 from being excessively stretched to generate pinholes during the stamping process, thereby improving the stamping forming performance of the aluminum-plastic film formed by the polypropylene film 1, in addition, the polypropylene film 1 can enhance the ability of the polypropylene film 1 to resist the penetration of polar solvents in electrolyte, so that the aluminum-plastic film prepared has good electrolyte resistance, and the polypropylene film 1 has good thermal stability, ensures the bonding strength between the layers of the aluminum-plastic film, and the aluminum-plastic film prepared has good high-temperature resistance. The aluminum-plastic film prepared from the polypropylene film 1 is applied to the battery, which helps to improve the energy density and safety performance of the battery.

[0042] The present application does not limit the specific thickness ratio of each layer in the polypropylene film 1, which can be adjusted according to actual needs. For example, in some embodiments, the thickness ratio of the heat-sealing layer 13 is 5% to 20%, for example 5%, 8%, 10%, 12%, 15%, 20% or a range consisting of any two of them, based on the thickness of the polypropylene film 1, the thickness ratio of the core layer 11 is 60% to 90%, for example 60%, 70%, 75%, 80%, 85%, 90% or a range consisting of any two of them, and the thickness ratio of the corona layer 12 is 5% to 20%, for example 5%, 8%, 10%, 12%, 15%, 20% or a range consisting of any two of them. Among them, the thickness of the core layer 11 accounts for 60% to 90% of the thickness of the entire polypropylene film 1, which is an important part of the aluminum-plastic film, and its performance directly affects the performance and quality of the aluminum-plastic film. By limiting the thickness ratio of each layer, the yield strength and tensile strength of the polypropylene film 1 can be improved.

[0043] The mass content of the rubber phase in the first polypropylene is 15% to 25%, and in some embodiments, the mass content of ethylene in the rubber phase of the first polypropylene is 20% to 40%, that is, the mass of ethylene in the rubber phase accounts for 20% to 40% of the total mass of the rubber phase, for example 20%, 25%, 30%, 35%, 40% or a range consisting of any two of them. By limiting the mass ratio of ethylene, the comprehensive performance of the polypropylene film 1 can be further improved.

[0044] It should be noted that the first polypropylene sample can be analyzed by infrared spectroscopy (FTIR) to identify the characteristic absorption peaks of the rubber phase and the characteristic absorption peaks of the ethylene group, and by quantitatively analyzing the intensities of these peaks, the content of the rubber phase and the content of ethylene in the rubber phase can be calculated.

[0045] The present application does not limit the specific mass content of each component in the material forming the core layer 11, which can be adjusted according to actual needs. In some embodiments, the mass content of the first polyolefin elastomer in the material forming the core layer 11 is ≤ 30%, and in some preferred embodiments, the mass content of the first polypropylene in the material forming the core layer 11 is 70% to 95%, for example, 70%, 75%, 80%, 85%, 90%, 95%, or a range consisting of any two of them, and the mass content of the first polyolefin elastomer is 5% to 30%, for example, 5%, 10%, 15%, 20%, 25%, 30%, or a range consisting of any two of them.

[0046] In the specific implementation of the present application, the heat sealing layer 13 is directly in contact with the battery cell, which is used to ensure that the aluminum plastic film can be tightly bonded with the battery cell during the heat sealing process to form a sealed package.

[0047] In some embodiments, the material forming the heat sealing layer 13 includes a second polypropylene and a second polyolefin elastomer, wherein the mass content of the second polypropylene is 90% to 97%, for example, 90%, 92%, 95%, 97%, or a range consisting of any two of them, and the mass content of the second polyolefin elastomer is 3% to 10%, for example, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of them. The melting point of the second polyolefin elastomer is < the melting point of the first polyolefin elastomer, which can significantly reduce the heat sealing temperature and improve the heat sealing strength to meet the packaging requirements of the battery. The introduction of the second polyolefin elastomer in the heat sealing layer 13 helps to further improve the draw forming performance and reduce the heat sealing temperature to improve the heat sealing strength.

[0048] The second polypropylene is a thermoplastic plastic that includes a polypropylene matrix polymerized from propylene monomers. The second polyolefin elastomer can be a polymer copolymerized from ethylene and α-olefins such as 1-butene, 1-hexene, etc. In some preferred embodiments, the melting point of the second polyolefin elastomer is 50 to 80°C, for example, 50°C, 60°C, 70°C, 80°C, or a range consisting of any two of them. By limiting the melting point of the second polyolefin elastomer to 50 to 80°C, the packaging temperature can be further reduced and the packaging strength can be improved.

[0049] It should be noted that the specific types of the first polyolefin elastomer and the second polyolefin elastomer can be the same or different, as long as they meet the above-mentioned melting point requirements. For example, in some embodiments, the first polyolefin elastomer and the second polyolefin elastomer are each independently selected from at least one of ethylene-α-olefin elastomers and propylene-α-olefin elastomers.

[0050] In some preferred embodiments, the first polyolefin elastomer is a copolymer of propylene monomers and ethylene monomers, or the first polyolefin elastomer is a copolymer of propylene monomers and 1-butene monomers, the second polyolefin elastomer is a copolymer of ethylene monomers and 1-butene monomers, or the second polyolefin elastomer is a copolymer of ethylene monomers and 1-octene monomers.

[0051] In some preferred embodiments, the first polyolefin elastomer has a weight average molecular weight of 1.5-2.5 million, and the second polyolefin elastomer has a weight average molecular weight of 1.2-2 million.

[0052] The present application does not limit the specific type of polypropylene as long as the rubber phase and the ethylene content in the first polypropylene are ensured. In some embodiments, the first polypropylene is a block copolymer polypropylene, and the second polypropylene is a binary random copolymer polypropylene or a ternary random copolymer polypropylene. Specifically, when the first polypropylene is a block copolymer polypropylene, the first polypropylene is a block copolymer of propylene monomers and ethylene monomers, and the first polypropylene includes a propylene homopolymer, i.e., a polypropylene matrix, and an ethylene-propylene rubber, which constitutes the total amount of the rubber phase in the first polypropylene. When the second polypropylene is a binary random copolymer polypropylene, the second polypropylene can be a random copolymer of propylene monomers and other olefin monomers, such as ethylene monomers or butene monomers; when the second polypropylene is a ternary random copolymer polypropylene, the second polypropylene can be a random copolymer of ethylene monomers, propylene monomers, and butene monomers. By limiting the specific types of the first polypropylene and the second polypropylene, the comprehensive performance of the polypropylene film 1 can be further improved.

[0053] In some preferred embodiments, the first polypropylene has a weight average molecular weight of 2-5 million, such as 2 million, 2.5 million, 3 million, 3.5 million, 4 million, 4.5 million, 5 million, or a range defined by any two of them, and the second polypropylene has a weight average molecular weight of 2-4 million, such as 2 million, 2.5 million, 3 million, 3.5 million, 4 million, or a range defined by any two of them.

[0054] The present application does not limit the material forming the corona layer 12, which can be a conventional polypropylene material in the art. For example, in some embodiments, the material forming the corona layer 12 includes a third polypropylene, and the third polypropylene includes a binary random copolymer polypropylene, i.e., the third polypropylene is a random copolymer of propylene monomers and other olefin monomers, such as ethylene monomers or butene monomers.

[0055] In some preferred embodiments, the third polypropylene has a weight average molecular weight of 2-4 million, such as 2 million, 2.5 million, 3 million, 3.5 million, 4 million, or a range defined by any two of them.

[0056] As Figure 2 shown in the second aspect of the present application, an aluminum-plastic film is provided, the aluminum-plastic film comprising an inner layer, an aluminum foil layer 2 and an outer layer 3 which are sequentially stacked, the inner layer being the polypropylene film 1 for aluminum-plastic film provided in the first aspect, the corona layer 12 of the polypropylene film 1 being attached to one surface of the aluminum foil layer 2, and the other surface of the aluminum foil layer 2 being attached to the outer layer 3.

[0057] Specifically, the polypropylene film 1 for aluminum-plastic film comprises a heat-sealing layer 13, a core layer 11 and a corona layer 12 which are sequentially stacked, and in the aluminum-plastic film, the corona layer 12 is attached to the aluminum foil layer 2 to play a bonding role. It can also be understood that the aluminum-plastic film comprises a corona layer 12, a core layer 11, a heat-sealing layer 13, an aluminum foil layer 2 and an outer layer 3 which are sequentially stacked.

[0058] The polypropylene film 1 can be attached to one surface of the aluminum foil layer 2 by heat bonding or gluing. The polypropylene film 1 serves as the inner surface of the aluminum-plastic film and will be in contact with the electrolyte and the battery cell after packaging. The outer layer 3 can be attached to the other surface of the aluminum foil layer 2 by heat bonding or gluing and serves as the outer surface of the aluminum-plastic film and will be in contact with the air outside after packaging. Due to the inclusion of the above-mentioned polypropylene film 1 with excellent performance, the aluminum-plastic film of the present application has excellent deep-drawing performance, high-temperature resistance and electrolyte resistance and can be used as a soft packaging material for battery cells. In some embodiments, the peeling force of the inner layer of the aluminum-plastic film at 120°C is greater than 3N / 15mm.

[0059] In some embodiments, the thickness ratio of the polypropylene film 1, the aluminum foil layer 2 and the outer layer 3 is (10-40):(20-80):(10-40).

[0060] The third aspect of the present application provides a battery, the battery comprising a battery cell and the aluminum-plastic film provided in the second aspect, the aluminum-plastic film being used for packaging the battery cell.

[0061] The aluminum-plastic film of the present application is mainly applied to lithium batteries. Specifically, the battery cell of the present application can be a lithium battery cell, and after packaging, the inner layer of the aluminum-plastic film is closely attached to the battery cell, and the polypropylene film 1 is actually in contact with the electrolyte. It can be understood that the corona layer 12 is closely attached to the battery cell. Due to the inclusion of the above-mentioned aluminum-plastic film with excellent performance, the battery of the present application has excellent energy density and safety performance, and good packaging performance.

[0062] The present application will be further described in detail below in conjunction with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0063] Example 1

[0064] I. Preparation of polypropylene film 1

[0065] S1, melt-mixing a first polypropylene (block copolymerized polypropylene) and a first polyolefin elastomer (propylene-ethylene polyolefin elastomer) at a mass ratio of 80:20 at a temperature of 260°C to obtain a core layer slurry;

[0066] S2, melt-mixing a second polypropylene (dual random copolymerized polypropylene) and a second polyolefin elastomer (ethylene-butene polyolefin elastomer) at a mass ratio of 90:10 at a temperature of 250°C to obtain a heat-seal layer slurry;

[0067] S3, melting a third polypropylene (dual random copolymerized polypropylene) at a temperature of 250°C to obtain a corona layer slurry;

[0068] S4, co-extruding the heat-seal layer slurry, the core layer slurry and the corona layer slurry at a temperature of 270°C to obtain a polypropylene film 1 composed of a heat-seal layer 13, a core layer 11 and a corona layer 12, the thickness of the heat-seal layer 13, the core layer 11 and the corona layer 12 being 6 μm, 28 μm and 6 μm respectively.

[0069] The first polypropylene is a block copolymerized polypropylene, the mass content of the rubber phase is 15%, the mass content of ethylene in the rubber phase is 20%, and the weight average molecular weight of the first polypropylene is 350,000;

[0070] The second polypropylene is a dual random copolymerized polypropylene, and the weight average molecular weight is 230,000;

[0071] The third polypropylene is a dual random copolymerized polypropylene, and the weight average molecular weight is 230,000;

[0072] The first polyolefin elastomer is a propylene-ethylene elastomer, the melting point is 100°C, and the weight average molecular weight is 150,000;

[0073] The second polyolefin elastomer is an ethylene-1-butene elastomer, the melting point is 60°C, and the weight average molecular weight is 120,000.

[0074] II. Preparation of the aluminum-plastic film

[0075] An aluminum foil with a thickness of 40 μm is selected as the aluminum foil layer 2;

[0076] The corona layer 12 of the polypropylene film 1 is arranged opposite to the aluminum foil layer 2, and the polypropylene film 1 is hot-bonded to one surface of the aluminum foil layer 2 at a temperature of 110°C; a composite biaxially stretched nylon film is coated on the other surface of the aluminum foil layer 2 as an outer layer film, and after aging at a temperature of 60°C for 5 days, an outer layer 3 with a thickness of 25 μm is formed, thereby obtaining the aluminum-plastic film of the present example.

[0077] Example 2

[0078] The mass content of the rubber phase in the first polypropylene is 20%, the mass content of ethylene in the rubber phase is 30%, and the weight average molecular weight of the first polypropylene is 300,000, compared with Example 1.

[0079] Example 3

[0080] The mass content of the rubber phase in the first polypropylene is 25%, the mass content of ethylene in the rubber phase is 40%, and the weight average molecular weight of the first polypropylene is 250,000, compared with Example 1.

[0081] Example 4

[0082] The melting point of the first polyolefin elastomer is 120°C, and the weight average molecular weight is 160,000, compared with Example 1.

[0083] Example 5

[0084] The melting point of the first polyolefin elastomer is 160°C, and the weight average molecular weight is 180,000, compared with Example 1.

[0085] Example 6

[0086] The thicknesses of the heat-seal layer 13, the core layer 11, and the corona layer 12 are 8 μm, 24 μm, and 8 μm, respectively, compared with Example 1.

[0087] Example 7

[0088] The thicknesses of the heat-seal layer 13, the core layer 11, and the corona layer 12 are 2 μm, 36 μm, and 2 μm, respectively, compared with Example 1.

[0089] Example 8

[0090] The mass ratio of the first polypropylene to the first polyolefin elastomer is 70:30, compared with Example 1.

[0091] Example 9

[0092] The mass ratio of the first polypropylene to the first polyolefin elastomer is 95:5, compared with Example 1.

[0093] Example 10

[0094] The melting point of the second polyolefin elastomer is 50°C, and the weight average molecular weight is 100,000, compared with Example 1.

[0095] Example 11

[0096] The melting point of the second polyolefin elastomer is 80°C, and the weight average molecular weight is 150,000, compared with Example 1.

[0097] Example 12

[0098] The second polyolefin elastomer has a melting point of 100°C and a weight average molecular weight of 180,000.

[0099] Comparative Example 1

[0100] The difference from Example 1 is that the core layer 11 does not contain the first polyolefin elastomer.

[0101] Comparative Example 2

[0102] The difference from Example 1 is that the first polypropylene has a rubber phase content of 10%, the first polyolefin elastomer has a melting point of 80°C, and the first polypropylene has a weight average molecular weight of 480,000.

[0103] Comparative Example 3

[0104] The difference from Example 1 is that the first polypropylene has a rubber phase content of 10%, the rubber phase has an ethylene content of 15%, and the first polypropylene has a weight average molecular weight of 420,000.

[0105] Comparative Example 4

[0106] The difference from Example 1 is that the first polypropylene has a rubber phase content of 30%, the rubber phase has an ethylene content of 20%, and the first polypropylene has a weight average molecular weight of 280,000.

[0107] Comparative Example 5

[0108] The difference from Example 1 is that the first polyolefin elastomer has a melting point of 80°C and a weight average molecular weight of 1,200,000.

[0109] Comparative Example 6

[0110] The difference from Example 1 is that the first polyolefin elastomer has a melting point of 170°C and a weight average molecular weight of 230,000.

[0111] Test Example

[0112] 1. Punch deep forming property

[0113] An aluminum plastic film was cut into a 110 mm (TD) * 130 mm (MD) sample, and cold punch forming was performed using a 60 mm (TD) * 75 mm (MD) mold with a forming depth of 5.0 mm. The degree of whitening on the inner side of the corner edge was observed, and slight whitening was marked as √, severe whitening was marked as X, and the presence of microcracks was marked as XX.

[0114] 2. High temperature resistance

[0115] Cut the aluminum-plastic film into 15mm (TD) * 100mm (MD) sample, and use the universal testing machine to test the peeling strength between the inner layer CPP and the aluminum foil layer at 120℃, the test method is T-type peeling, and the tensile speed is 100mm / min.

[0116] 3. Electrolyte resistance

[0117] Cut the aluminum-plastic film into 15mm (TD) * 100mm (MD) sample, and place it in a PP bottle containing electrolyte, and add 1000ppm water, and place the PP bottle containing the sample in a 60℃ oven, and take it out after standing for 14 days, use the universal testing machine to test the peeling strength between the inner layer CPP and the aluminum foil layer at room temperature, the test method is T-type peeling, and the tensile speed is 100mm / min.

[0118] The test results are shown in Table 1.

[0119] Table 1

[0120] Number Punching performance High temperature resistance N / 15mm Electrolyte resistance N / 15mm Example 1 √ 4.0 8.5 Example 2 √ 3.9 8.6 Example 3 √ 3.8 8.8 Example 4 √ 4.5 8.2 Example 5 √ 5.0 8.3 Example 6 √ 4.8 8.0 Example 7 √ 5.2 7.8 Example 8 √ 4.5 9 Example 9 √ 3.4 7.5 Example 10 √ 3.1 8 Example 11 √ 4.2 8.1 Example 12 √ 3 7 Comparative Example 1 ×× 0.5 2.8 Comparative Example 2 ×× 1.5 4.7 Comparative Example 3 × 3.5 6.1 Comparative Example 4 √ 2.5 4.8 Comparative Example 5 × 2.5 3.5 Comparative Example 6 × 3.8 6.8

[0121] According to Table 1, the material of the polypropylene film forming the core layer in the examples meets: the mass content of the rubber phase in the first polypropylene is 15% to 25%, and the melting point of the first polyolefin elastomer is 100 to 160℃, while the core layer of Comparative Example 1 does not add the first polyolefin elastomer, Comparative Example 2 does not meet the mass content of the rubber phase in the first polypropylene being 15% to 25% and the melting point of the first polyolefin elastomer being 100 to 160℃, Comparative Examples 3 to 4 do not meet the mass content of the rubber phase in the first polypropylene being 15% to 25%, Comparative Examples 5 to 6 do not meet the melting point of the first polyolefin elastomer being 100 to 160℃, the aluminum-plastic film of Examples 1 to 11 has excellent deep draw forming performance, the high temperature peeling strength is greater than 3N / 15mm, and the electrolyte resistance is greater than 7N / 15mm, the performance qualified data index has good high temperature resistance and electrolyte resistance, and the effect of the comparative examples is not as good as the examples. Therefore, by introducing the polypropylene film meeting the above parameters, the deep draw forming performance, high temperature resistance and electrolyte resistance of the aluminum-plastic film can be significantly improved.

[0122] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A polypropylene film for an aluminum laminate film, characterized by, The polypropylene film (1) comprises a heat-sealing layer (13), a core layer (11) and a corona layer (12) which are sequentially stacked. The material forming the core layer (11) comprises a first polypropylene and a first polyolefin elastomer, the mass content of the rubber phase in the first polypropylene is 15% to 25%, and the melting point of the first polyolefin elastomer is 100 to 160℃. The weight average molecular weight of the first polypropylene is 2 to 5 million, the weight average molecular weight of the first polyolefin elastomer is 1.5 to 2.5 million, and the rubber phase is a copolymer polymerized by ethylene monomer and propylene monomer.

2. The polypropylene film according to claim 1, characterized in that, The thickness of the heat-sealing layer (13) accounts for 5% to 20% of the thickness of the polypropylene film (1), the thickness of the core layer (11) accounts for 60% to 90% of the thickness of the polypropylene film (1), and the thickness of the corona layer (12) accounts for 5% to 20% of the thickness of the polypropylene film (1).

3. The polypropylene film according to claim 1, characterized in that, The mass content of ethylene in the rubber phase of the first polypropylene is 20% to 40%; and / or, The mass content of the first polyolefin elastomer in the material forming the core layer (11) is ≤30%.

4. The polypropylene film according to claim 1, characterized in that, The mass content of the first polypropylene in the material forming the core layer (11) is 70% to 95%, and the mass content of the first polyolefin elastomer is 5% to 30%.

5. The polypropylene film according to any one of claims 1 to 4, characterized in that, The material forming the heat-sealing layer (13) comprises a second polypropylene and a second polyolefin elastomer. The mass content of the second polypropylene in the material forming the heat-sealing layer (13) is 90% to 97%, and the mass content of the second polyolefin elastomer is 3% to 10%. The melting point of the second polyolefin elastomer is < the melting point of the first polyolefin elastomer.

6. The polypropylene film according to claim 5, characterized in that, The melting point of the second polyolefin elastomer is 50 to 80℃.

7. The polypropylene film according to claim 5, characterized in that, The first polyolefin elastomer and the second polyolefin elastomer are each independently selected from at least one of ethylene-α-olefin elastomer and propylene-α-olefin elastomer.

8. The polypropylene film according to claim 5, characterized in that, The first polyolefin elastomer is a copolymer of propylene monomer and ethylene monomer, or the first polyolefin elastomer is a copolymer of propylene monomer and 1-butene monomer; The second polyolefin elastomer is a copolymer of ethylene monomer and 1-butene monomer, or the second polyolefin elastomer is a copolymer of ethylene monomer and 1-octene monomer; The weight average molecular weight of the second polyolefin elastomer is 1.2 to 2 million.

9. The polypropylene film according to claim 5, characterized in that, The first polypropylene is a block copolymerization polypropylene, and the second polypropylene is a binary random copolymerization polypropylene or a ternary random copolymerization polypropylene.

10. The polypropylene film according to claim 5, characterized in that, The first polypropylene is a block copolymer polymerized by propylene monomer and ethylene monomer; The second polypropylene is a random copolymer polymerized by propylene monomer and ethylene monomer, or a random copolymer polymerized by propylene monomer and butene monomer, or a random copolymer polymerized by ethylene monomer, propylene monomer and butene monomer; The weight average molecular weight of the second polypropylene is 2 to 4 million.

11. The polypropylene film according to claim 5, characterized in that, The material forming the corona layer (12) comprises a third polypropylene, and the third polypropylene is a binary random copolymerization polypropylene.

12. The polypropylene film according to claim 11, characterized in that, The third polypropylene is a binary random copolymer polymerized from propylene monomers and ethylene monomers; or the third polypropylene is a binary random copolymer polymerized from propylene monomers and butylene monomers. The weight average molecular weight of the third polypropylene is 200-400 thousand.

13. An aluminum laminate characterized by comprising: The aluminum-plastic film comprises an inner layer, an aluminum foil layer (2) and an outer layer (3) which are sequentially stacked; wherein the inner layer is the polypropylene film (1) for aluminum-plastic film according to any one of claims 1 to 12, the corona layer (12) of the polypropylene film (1) is attached to one surface of the aluminum foil layer (2), and the other surface of the aluminum foil layer (2) is attached to the outer layer (3).

14. A battery, characterized by The battery comprises a battery cell and the aluminum-plastic film according to claim 13, and the aluminum-plastic film is used for packaging the battery cell.

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