Polypropylene film and aluminum plastic film containing same

Abstract

The invention discloses a polypropylene film and an aluminum plastic film containing the polypropylene film, the polypropylene film comprises a composite layer and a core layer, the core layer is located on one side of the composite layer in the thickness direction, and the composite layer comprises 65-85 parts by weight of a first polyolefin blend; 5 to 20 parts by weight of a first cycloolefin polymer; the core layer includes a second polyolefin blend. According to the polypropylene film provided by the invention, by adding the first cycloolefin polymer into the composite layer, interlaminar molecular winding of the co-extruded CPP film is promoted, so that the interlaminar stability of the CPP film is enhanced, the CPP film does not generate self layering when being stripped from an aluminum foil and packaged and stripped, and the use safety of the aluminum plastic film is improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a polypropylene film and an aluminum-plastic film containing the same. Background Art

[0002] Common dry aluminum-plastic film is generally composed of three main layers of materials, namely nylon (PA) / aluminum foil / cast polypropylene (CPP) film, which are bonded and composited with corresponding adhesives. Among them, CPP film, as the innermost material of aluminum-plastic film, has attracted more and more attention because it can better solve the problem of gas bloating in soft-pack lithium-ion secondary batteries. At the same time, the good electrolyte resistance, heat sealing performance, stamping formability, etc. of aluminum-plastic film need to be achieved by optimizing the relevant properties of the innermost CPP film. When the battery has safety hazards such as electrolyte leakage, gas bloating, etc., the soft-pack lithium battery will generally bulge first, or crack from the weak point of the seal. PA and aluminum foil have high strength themselves. In addition to adhesives, CPP film is the weak point of soft-pack lithium batteries. During use, CPP film may be delaminated, and electrolyte will penetrate through the gaps between the CPP film delaminations, resulting in electrolyte leakage, fire and other safety problems. Summary of the invention

[0003] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0004] In a first aspect, the present application provides a polypropylene film, comprising a composite layer and a core layer, wherein the core layer is located on one side of the composite layer in a thickness direction, and the composite layer comprises: a first polyolefin blend, 65 to 85 parts by weight; a first cycloolefin polymer, 5 to 20 parts by weight; and the core layer comprises a second polyolefin blend.

[0005] The polypropylene film proposed in the present application promotes the interlayer molecular entanglement of the co-extruded CPP film by adding a first cyclic olefin polymer into the composite layer, thereby enhancing the interlayer stability of the CPP film, so that the CPP film does not produce self-delamination when peeling off the aluminum foil and the packaging peeling, thereby improving the safety of the aluminum-plastic film.

[0006] According to some embodiments of the present application, the composite layer further comprises: 5 to 25 parts by weight of the first elastomer; 0.1 to 2 parts by weight of the first antioxidant; the core layer further comprises: 70 to 98 parts by weight of the second polyolefin blend; 10 to 20 parts by weight of the second elastomer; and 0.1 to 2 parts by weight of the second antioxidant. Thus, the toughness and anti-oxidation performance of the polypropylene film are improved.

[0007] According to some embodiments of the present application, the core layer further comprises: a second cycloolefin polymer, thereby further improving the interlayer stability of the polypropylene film.

[0008] According to some embodiments of the present application, the core layer further comprises: 5 parts by weight to 20 parts by weight of a second cycloolefin polymer, thereby further improving the interlayer stability of the polypropylene film.

[0009] According to some embodiments of the present application, the glass transition temperature T g The temperature is independently 65° C. to 140° C. Thus, the high temperature resistance and packaging strength of the polypropylene film are improved.

[0010] According to some embodiments of the present application, the first cycloolefin polymer and the second cycloolefin polymer independently include at least one of cycloolefin polymer (COP), cycloolefin polymer (COC), and cycloolefin polymer (CBC). Thus, the interlayer stability of the polypropylene film is improved.

[0011] According to some embodiments of the present application, the first polyolefin blend and the second polyolefin blend independently include at least one of block copolymer polypropylene, random copolymer polypropylene, and homopolymer polypropylene, thereby improving the electrolyte resistance of the polypropylene film.

[0012] According to some embodiments of the present application, a heat sealing layer is further included, and the heat sealing layer is located on a side of the core layer away from the composite layer, thereby improving the heat sealing performance of the aluminum-plastic film.

[0013] The second aspect of the present application provides an aluminum-plastic film, comprising the polypropylene film provided in the first aspect of the present application. Thus, the aluminum-plastic film has excellent heat-sealing performance and safety performance.

[0014] According to some embodiments of the present application, the aluminum-plastic film includes: an aluminum foil layer, the polypropylene film is located on one side of the aluminum foil layer; and a resin protective layer, the resin protective layer is located on a side of the aluminum foil layer away from the polypropylene film. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0016] Figure 1 A schematic structural diagram of a polypropylene film according to an embodiment of the present application is shown.

[0017] Figure 2 A schematic structural diagram of an aluminum-plastic film according to an embodiment of the present application is shown.

[0018] Reference numerals:

[0019] 11: polypropylene film; 111: composite layer; 112: core layer; 113: heat sealing layer; 1: aluminum-plastic film; 12: aluminum foil layer; 13: resin protective layer. DETAILED DESCRIPTION

[0020] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the document in this area or the product specification are used. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0021] After the CPP film with good cohesion is compounded to form an aluminum-plastic film, it can still maintain its own non-delamination even if it has a high interlayer peeling force with the aluminum foil; after the CPP film is packaged, the hand-tear peeling surface of the corresponding aluminum-plastic film is uniformly milky white on both sides. However, when the CPP film with poor cohesion is peeled off from the aluminum foil, the composite layer and the core layer are mostly separated. At the same time, the hand-tear peeling appearance of the corresponding aluminum-plastic film is whitish on one side, and the peeling interface is relatively messy, wire-drawn, and uneven.

[0022] This application proposes a polypropylene film (CPP film), referring to Figure 1 The polypropylene film 11 includes a composite layer 111 and a core layer 112. The core layer 112 is located on one side of the composite layer 111 in the thickness direction. The composite layer 111 includes: a first polyolefin blend, 65 to 85 parts by weight; a first cycloolefin polymer, 5 to 20 parts by weight; and the core layer includes a second polyolefin blend.

[0023] The polypropylene film proposed in the present application has a first cycloolefin polymer added to the composite layer. The rigid cycloolefin monomer copolymer segments in the first cycloolefin polymer can serve as physical crosslinking points to combine with other molecular chains to form strong molecular clusters through hydrogen bonds during melt co-extrusion into films, thereby improving the overall modulus and yield strength of the material, enhancing the mechanical properties and stability of the material, and preventing the CPP film from self-delamination under strong external forces, thereby improving the interlayer stability of the CPP film, preventing the CPP film from self-delamination when peeling off the aluminum foil and packaging peeling, thereby improving the safety of the aluminum-plastic film.

[0024] If the content of the first cycloolefin polymer is less than 5 parts by weight, the rigid cycloolefin monomer copolymer segments in the cycloolefin polymer in the system are relatively small, and the physical cross-linking points provided are relatively small, so that it cannot effectively combine with other molecular chains, and the effect of improving the interlayer stability is relatively poor; if the content of the first cycloolefin polymer is greater than 20 parts by weight, the rigidity of the composite layer is too strong, which will reduce the toughness of the CPP film and is not conducive to the deep punching of the aluminum-plastic film.

[0025] As an example, the content of the first cycloolefin-based polymer may be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, etc., or may be in a range consisting of any of the above values.

[0026] As an example, the content of the first polyolefin blend can be 65 parts by weight, 70 parts by weight, 75 parts by weight, 80 parts by weight, 85 parts by weight, etc., or can be a range consisting of any of the above values.

[0027] According to some embodiments of the present application, the composite layer includes: 65 to 85 parts by weight of the first polyolefin blend; 5 to 20 parts by weight of the first cycloolefin polymer; 5 to 25 parts by weight of the first elastomer; 0.1 to 2 parts by weight of the first antioxidant; the core layer includes: 70 to 98 parts by weight of the second polyolefin blend; 10 to 20 parts by weight of the second elastomer; 0.1 to 2 parts by weight of the second antioxidant. Thus, the toughness and antioxidant properties of the polypropylene film are improved.

[0028] As an example, the content of the first elastomer in the composite layer may be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, etc., or may be a range consisting of any of the above values.

[0029] As an example, the content of the first antioxidant in the composite layer can be 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, etc., or can be a range consisting of any of the above values.

[0030] As an example, the content of the second elastomer in the core layer can be 10 parts by weight, 13 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, etc., or can be a range consisting of any of the above values.

[0031] As an example, the content of the second antioxidant in the core layer can be 0.1 parts by weight, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, etc., or can be a range consisting of any of the above values.

[0032] According to some embodiments of the present application, the composite layer may further include a first auxiliary agent, wherein the first auxiliary agent includes at least one of a polymer processing aid, an antistatic agent, and a slip and opening agent.

[0033] As an example, the content of the first auxiliary agent in the composite layer can be 0-5 parts by weight, for example, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, etc., or can be a range consisting of any of the above values.

[0034] According to some embodiments of the present application, the core layer includes: 70 to 98 parts by weight of the second polyolefin blend, 5 to 20 parts by weight of the second cycloolefin polymer, 10 to 20 parts by weight of the second elastomer, and 0.1 to 2 parts by weight of the second antioxidant. Thus, adding the cycloolefin polymer to the composite layer and the core layer at the same time can improve the interlayer stability between the composite layer and the core layer, and further improve the interlayer stability of the polypropylene film.

[0035] As an example, the content of the second cycloolefin polymer in the core layer may be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, etc., or may be in a range consisting of any of the above values.

[0036] According to some embodiments of the present application, the core layer may further include a second auxiliary agent, wherein the second auxiliary agent includes at least one of a polymer processing aid, an antistatic agent, and a slip and opening agent.

[0037] As an example, the content of the second auxiliary agent in the core layer can be 0-2 parts by weight, for example, 0.5 parts by weight, 1 part by weight, 1.5 parts by weight, 2 parts by weight, etc., or can be a range consisting of any of the above values.

[0038] According to some embodiments of the present application, the glass transition temperature T g They are independently 65° C. to 140° C. Specifically, the glass transition temperatures of the first cycloolefin polymer and the second cycloolefin polymer may be the same or different.

[0039] By making the glass transition temperature of the first cycloolefin polymer and the second cycloolefin polymer within the above range, on the one hand, the high temperature resistance of the CPP film can be improved and the probability of the CPP film being delaminated under high temperature conditions can be reduced; on the other hand, by making the glass transition temperature within the above range, the heat transfer rate of the CPP film can be increased, the risk of the CPP film being difficult to melt quickly in the heat-sealed composite layer due to the excessively high glass transition temperature can be reduced, and the packaging strength of the CPP film can be improved. At the same time, the higher the glass transition temperature of the cycloolefin polymer, the higher the proportion of the rigid chain segment contained. By making the glass transition temperature within the above range, the CPP film has a suitable toughness, and the probability of cracks in the aluminum-plastic film during deep punching can be reduced.

[0040] As an example, the glass transition temperature T of the first cycloolefin polymer is g The temperature may be 65°C, 75°C, 85°C, 95°C, 105°C, 115°C, 125°C, 135°C, 140°C, etc., or may be within a range consisting of any of the above values.

[0041] As an example, the glass transition temperature T g The temperature may be 65°C, 75°C, 85°C, 95°C, 105°C, 115°C, 125°C, 135°C, 140°C, etc., or may be within a range consisting of any of the above values.

[0042] According to some embodiments of the present application, the first cycloolefin polymer and the second cycloolefin polymer independently include at least one of cycloolefin polymer (COP), cycloolefin polymer (COC), and cycloolefin polymer (CBC). Specifically, the first cycloolefin polymer and the second cycloolefin polymer can be the same or different. By adding cycloolefin polymers to the composite layer and the core layer at the same time, the interlayer stability of the polypropylene film is further improved.

[0043] According to some embodiments of the present application, the first polyolefin blend and the second polyolefin blend independently include at least one of block copolymer polypropylene, random copolymer polypropylene, and homopolymer polypropylene. Specifically, the first polyolefin blend and the second polyolefin blend may be the same or different. Thus, the electrolyte resistance of the polypropylene film is improved.

[0044] Thereby, the punching formability of the polypropylene film is improved.

[0045] According to some embodiments of the present application, reference Figure 1 The polypropylene film 11 further comprises a heat sealing layer 113, and the heat sealing layer 113 is located on a side of the core layer 112 away from the composite layer 111. Thus, the heat sealing performance of the aluminum-plastic film is improved.

[0046] The second aspect of the present application provides an aluminum-plastic film, comprising the polypropylene film provided in the first aspect of the present application. Thus, the aluminum-plastic film has excellent heat-sealing performance and safety performance.

[0047] According to some embodiments of the present application, reference Figure 2 The aluminum-plastic film 1 comprises: an aluminum foil layer 12 , the polypropylene film 11 is located on one side of the aluminum foil layer 12 ; and a resin protective layer 13 , the resin protective layer 13 is located on a side of the aluminum foil layer 12 away from the polypropylene film 11 .

[0048] As an example, the resin protection layer includes one or both of nylon and polyethylene terephthalate (PET) materials.

[0049] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the document in this area or the product specification are used. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0050] Example 1

[0051] The CPP film includes a composite layer, a core layer and a heat-sealing layer. The core layer is located between the composite layer and the heat-sealing layer. The composite layer includes:

[0052] Homopolymer polypropylene, 84.5 parts by weight;

[0053] The first elastomer, 10 parts by weight;

[0054] The first cyclic olefin polymer COC (T g is 100° C.), 5 parts by weight;

[0055] The first antioxidant, 0.5 parts by weight;

[0056] The core layer includes:

[0057] Block copolymer polypropylene, 84.5 parts by weight;

[0058] The second elastomer, 15 parts by weight;

[0059] The second antioxidant, 0.5 parts by weight;

[0060] The heat seal layer includes:

[0061] Block copolymer polypropylene, 84.5 parts by weight;

[0062] Elastomer, 15 parts by weight;

[0063] Antioxidant, 0.5 parts by weight.

[0064] Embodiment 2:

[0065] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: 20 parts by weight of a first cycloolefin polymer COC (Tg is 100°C).

[0066] Embodiment 3:

[0067] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: 12 parts by weight of a first cycloolefin polymer COC (Tg is 65°C).

[0068] Embodiment 4:

[0069] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: 12 parts by weight of a first cycloolefin polymer COC (Tg is 140°C).

[0070] Embodiment 5:

[0071] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: 5 parts by weight of a first cycloolefin polymer COP (Tg is 100° C.).

[0072] Embodiment 6:

[0073] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer includes: 20 parts by weight of a first cycloolefin polymer COP (Tg is 100°C).

[0074] Embodiment 7:

[0075] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer comprises: 12 parts by weight of a first cycloolefin polymer COP (Tg is 65°C).

[0076] Embodiment 8:

[0077] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer comprises: 12 parts by weight of a first cycloolefin polymer COP (Tg is 140°C).

[0078] Embodiment 9:

[0079] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: 5 parts by weight of a first cycloolefin polymer CBC (Tg is 100°C).

[0080] Embodiment 10:

[0081] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer includes: 20 parts by weight of a first cycloolefin polymer CBC (Tg is 100°C).

[0082] Embodiment 11:

[0083] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer includes: 12 parts by weight of a first cycloolefin polymer CBC (Tg is 65°C).

[0084] Embodiment 12:

[0085] The structure and composition of the CPP film are the same as those of Example 5, except that the composite layer includes: 12 parts by weight of a first cycloolefin polymer CBC (Tg is 140°C).

[0086] Embodiment 13:

[0087] The CPP film includes a composite layer, a core layer and a heat-sealing layer. The core layer is located between the composite layer and the heat-sealing layer. The composite layer includes:

[0088] Homopolymer polypropylene, 83.5 parts by weight;

[0089] The first elastomer, 10 parts by weight;

[0090] The first cyclic olefin polymer COC (T g is 100° C.), 5 parts by weight;

[0091] The first antioxidant, 0.5 parts by weight;

[0092] The core layer includes:

[0093] Block copolymer polypropylene, 79.5 parts by weight;

[0094] The second cyclic olefin polymer COC (T g is 100° C.), 5 parts by weight;

[0095] The second elastomer, 15 parts by weight;

[0096] The second antioxidant, 0.5 parts by weight;

[0097] The heat seal layer includes:

[0098] Block copolymer polypropylene, 84.5 parts by weight;

[0099] Elastomer, 15 parts by weight;

[0100] Antioxidant, 0.5 parts by weight.

[0101] Comparative Example 1

[0102] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: homopolypropylene, 89.5 parts by weight; a first elastomer, 10 parts by weight; and a first antioxidant, 0.5 parts by weight.

[0103] Comparative Example 2

[0104] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: homopolymer polypropylene, 86.5 parts by weight, a first cycloolefin polymer COC (T g 100° C.), 3 parts by weight, a first elastomer, 10 parts by weight, and a first antioxidant, 0.5 parts by weight.

[0105] Comparative Example 3

[0106] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: homopolymer polypropylene, 59.5 parts by weight, a first cycloolefin polymer COC (T g120° C.), 30 parts by weight, a first elastomer, 10 parts by weight, and a first antioxidant, 0.5 parts by weight.

[0107] Comparative Example 4

[0108] The structure and composition of the CPP film are the same as those of Example 1, except that the composite layer comprises: homopolymer polypropylene, 74.5 parts by weight, a first cycloolefin polymer COC (T g 180° C.), 15 parts by weight, a first elastomer, 10 parts by weight, and a first antioxidant, 0.5 parts by weight.

[0109] In Examples 1-13 and Comparative Examples 1-4, the raw materials of the composite layer, core layer and heat sealing layer were mixed respectively according to the above-mentioned weight ratio, and put into the corresponding hopper of the three-layer co-extrusion casting machine, and the thickness ratio of the three layers was set to 1:4:1. A 50μm CPP film was made by co-extrusion casting process, and the composite surface was corona treated.

[0110] The CPP films of Examples 1-13 and Comparative Examples 1-4 are compounded on the aluminum foil surface of PA / Al, and the aluminum-plastic film can be obtained after the glue is cured.

[0111] The peeling force between the CPP film and the aluminum foil was tested at 25°C and 85°C (tested at a speed of 100 mm / min) and the peeling appearance. The maximum punching depth at which the aluminum-plastic film was not broken was tested (a 57mm×98mm mold was used for a 5-9mm punching depth experiment). The aluminum-plastic film was heat-sealed at 185°C, 0.3Mpa, and 3s. The packaging peeling force was tested at 25°C and 85°C (tested at a speed of 300mm / min), and the hand-tear peeling appearance was observed.

[0112] The test results of the aluminum-plastic films in Examples 1 to 13 and Comparative Examples 1 to 4 are shown in Table 1.

[0113] Table 1

[0114]

[0115]

[0116] It can be seen from Table 1 that adding a certain amount of cycloolefin polymer (COP), cycloolefin copolymer (COC) or cyclic block copolymer (CBC) to the composite layer of CPP film is a good solution to solve the problem of self-delamination when CPP film is peeled off from aluminum foil and the poor appearance of CPP film peeling off corresponding to aluminum-plastic film packaging.

[0117] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A polypropylene film, characterized in that It comprises a composite layer and a core layer, wherein the core layer is located on one side of the composite layer in the thickness direction, and the composite layer comprises: The first polyolefin blend, 65 to 85 parts by weight; The first cycloolefin polymer, 5 to 20 parts by weight; The core layer includes a second polyolefin blend.

2. The polypropylene film according to claim 1, characterized in that The composite layer further comprises: The first elastomer, 5 to 25 parts by weight; The first antioxidant, 0.1 to 2 parts by weight; The core layer also includes: The second polyolefin blend, 70 parts by weight to 98 parts by weight; The second elastomer, 10 to 20 parts by weight; The second antioxidant is 0.1 to 2 parts by weight.

3. The polypropylene film according to claim 2, characterized in that The core layer further comprises: a second cycloolefin polymer.

4. The polypropylene film according to claim 3, characterized in that The core layer also includes: The second cycloolefin polymer is 5 parts by weight to 20 parts by weight.

5. The polypropylene film according to claim 3 or 4, characterized in that The glass transition temperature T of the first cycloolefin polymer and the second cycloolefin polymer g are independently 65°C-140°C.

6. The polypropylene film according to claim 3 or 4, characterized in that The first cyclic olefin polymer and the second cyclic olefin polymer each independently include at least one of COP, COC, and CBC.

7. The polypropylene film according to claim 1, characterized in that The first polyolefin blend and the second polyolefin blend independently include at least one of block copolymer polypropylene, random copolymer polypropylene and homopolymer polypropylene.

8. The polypropylene film according to claim 1, characterized in that The invention also comprises a heat sealing layer, wherein the heat sealing layer is located on a side of the core layer away from the composite layer.

9. An aluminum-plastic film, characterized in that: The invention comprises the polypropylene film according to any one of claims 1 to 8.

10. The aluminum-plastic film according to claim 9, characterized in that: include: An aluminum foil layer, wherein the polypropylene film is located on one side of the aluminum foil layer; A resin protective layer is located on a side of the aluminum foil layer away from the polypropylene film.

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