Core layer, cpp film, method for preparing the same, and al-plastic film

Abstract

The application discloses a core layer, a CPP film, a preparation method of the core layer and an aluminum-plastic film. The first raw material for forming the core layer comprises 51-88% of block copolymerized polypropylene and 2-15% of high-density polyethylene. The block copolymerized polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymerized polypropylene is 0.88-0.92 g / cm 3 . The melt index is 1-6 g / 10 min, and the melting point is 150-163 DEG C. The density of the high-density polyethylene is 0.955-0.97 g / cm 3 . The melt index is 6-14 g / 10 min, and the melting point is 128-140 DEG C. The core layer is used for preparing the CPP film, and the CPP film has good permeation resistance, impact resistance, tensile strength, elongation at break and elastic modulus.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery packaging materials, and particularly relates to the core layer, CPP film, preparation method thereof, and aluminum-plastic film. Background Technology

[0002] Aluminum-plastic film is a composite flexible packaging material used for encapsulating lithium-ion batteries. It is composed of an outer layer of nylon (or PET, etc.), a middle layer of aluminum foil, and an inner layer of CPP film bonded together with an adhesive. This three-layer structure endows aluminum-plastic film with multiple properties such as puncture resistance, high barrier properties, electrolyte resistance, high-temperature insulation, and high cold stamping formability. The CPP film, as the inner heat-sealing layer, not only requires good heat-sealing adhesion but also needs to prevent leaked electrolyte from corroding the aluminum foil, ensuring the safety and stability of the battery. CPP film, or cast polypropylene film, is a non-stretched, non-oriented planar extruded film, generally composed of a heat-sealing layer, a core layer, and a composite layer. The core layer of CPP film is mostly made of homopolymer because homopolymer has excellent rigidity, which can meet the film's requirements for support performance. At the same time, the core layer material accounts for 60% to 70% of the total film weight, and has a significant impact on the overall performance of the film.

[0003] As the intermediate layer in a multilayer composite film, the core layer plays a crucial role in providing the film's mechanical properties and structural support. However, in existing technologies for producing multilayer co-extruded films, the core layer process faces a series of challenges and problems. The selection of core layer materials requires comprehensive consideration of the film's permeability resistance, tensile strength, elongation at break, elastic modulus, impact resistance, and cost control. Existing materials often fail to meet all these requirements simultaneously, necessitating trade-offs among various properties. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the core layer of this invention is used to prepare CPP membranes, which possess excellent permeability resistance, impact resistance, tensile strength, elongation at break, and elastic modulus.

[0005] The purpose of this invention is to provide a core layer, wherein the first raw material forming the core layer, by weight percentage, 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℃.

[0006] In some embodiments of the present invention, the first 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℃.

[0007] In some embodiments of the present invention, the first raw material further includes 0.2-4% of an erucamide-type slip agent.

[0008] Another object of the present invention is to provide a CPP film comprising a heat-sealing layer, a core layer and a composite layer stacked sequentially.

[0009] In some embodiments of the present invention, the second raw material of the composite layer, by mass percentage, comprises 95-100% first homopolymer polypropylene and 0-5% silica opening agent, wherein 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℃.

[0010] In some embodiments of the present invention, the third raw material of the heat-sealing layer, by weight percentage, comprises 58-82% random copolymer polypropylene and 10-30% 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 / 10min, and the melting point is 120~140℃; 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℃.

[0011] In some embodiments of the present invention, the third raw material further includes 0.5-6% silica opening agent.

[0012] In some embodiments of the present invention, the third raw material further includes 0.5-6% of an erucamide-type slip agent.

[0013] In one embodiment of the present invention, the thickness percentages of the heat-sealing layer, the core layer, and the composite layer in the CPP film 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%.

[0014] In some embodiments of the present invention, the thickness of the CPP film is 30~100um.

[0015] Another objective of this invention is to provide a method for preparing the CPP film, wherein a heat-sealing layer, a core layer, and a composite layer are sequentially stacked using a multilayer co-extrusion casting technique.

[0016] Another object of the present invention is to provide an aluminum-plastic film, including a CPP film, wherein the CPP film is the aforementioned CPP film.

[0017] 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.

[0018] In some embodiments of the present invention, the thickness of the PET layer is 10~14 μm.

[0019] In some embodiments of the present invention, the thickness of the nylon layer is 20~30 μm.

[0020] In some embodiments of the present invention, the thickness of the aluminum foil layer is 40~50um.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The block copolymer polypropylene and high-density polyethylene used in this invention are used to form the core layer, so that the prepared CPP membrane has good permeation resistance.

[0023] (2) The block copolymer polypropylene, high-density polyethylene and polyolefin elastomer used in this invention are used to form the core layer, so that the prepared CPP film has good impact resistance.

[0024] (3) The core layer hybrid composite material used in this invention enables the prepared CPP film to have good tensile strength, elongation at break and elastic modulus. Attached Figure Description

[0025] Figure 1 The stamping effect of the CPP film in Example 1 is shown.

[0026] Figure 2 The stamping effect of the CPP film in Example 4 is shown. 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 / 10 min, and the melting point is 140℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index is 6g / 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 / 10 min, and the melting point is 150℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 128℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 g / cm³. 3 The melt index is 6g / 10min, and the melting point is 60℃;

[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 14g / 10min, and the melting point is 160℃;

[0034] According to the mass percentage, the raw materials of the heat-sealing layer, core layer and composite layer are melted at high temperature in the screw according to the above requirements, and fed into the three extruders corresponding to the three-layer co-extrusion casting machine. The thickness percentage of the three layers is set to 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 90kg / h. The extruder temperature for forming the core layer is 180℃ and the extrusion rate is 400kg / h. The extruder temperature for forming the composite layer is 180℃ and the extrusion rate is 90kg / h. The film is cooled and shaped on the smooth roller at a temperature of 20~60℃. After stretching by each guide roller, tempering treatment, corona treatment, thickness detection, online defect monitoring, flash removal, and winding, the production line speed is 50m / min and the winding tension is 5kg, 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 core layer material and the set thickness percentage of the three layers; otherwise, they are the same as in Example 1. By mass percentage, the core layer material in this example consists of: 51% block copolymer polypropylene, 15% high-density polyethylene, 30% polyolefin elastomer, and 4% 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 / 10 min, and the melting point is 150℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 128℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 g / cm³. 3 The melt index was 6 g / 10 min and the melting point was 60 °C; 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 core layer material 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 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 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℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 128℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 g / cm³. 3 The melt index was 6 g / 10 min and the melting point was 60 °C; 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 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 1 g / 10 min, and the melting point is 163℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 128℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 g / cm³. 3 The melt index is 5g / 10min, and the melting point is 95℃.

[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: 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 its density is 0.88 g / cm³. 3 The melt index is 1 g / 10 min, and the melting point is 163℃; the density of the high-density polyethylene is 0.955 g / cm³. 3 The melt index is 6 g / 10 min, and the melting point is 128℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.9 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 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 6g / 10min and a melting point of 166℃.

[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 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 6g / 10min and the melting point is 170℃.

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

[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 material, homopolymer polypropylene, used to form the heat-sealing layer. Otherwise, it is the same as Example 1. The density of the homopolymer polypropylene used to form the heat-sealing layer in this example is 0.89 g / cm³. 3 The melt index is 12g / 10min and the melting point is 155℃.

[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 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 12 g / 10 min, and the melting point is 120℃; the density of homopolymer polypropylene is 0.88 g / cm³. 3 The melt index is 14g / 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 structure of the block copolymer polypropylene used to form the core layer; otherwise, they are the same as in Example 1. In this comparative example, the block copolymer polypropylene used to form the core layer is an ethylene-propylene copolymer, and the density of the block copolymer polypropylene is 0.9 g / cm³. 3 The melt index is 9g / 10min and the melting point is 145℃.

[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 high-density polyethylene used to form the core layer is different; otherwise, it is the same as Example 1. The density of the high-density polyethylene used to form the core layer in this comparative example is 0.97 g / cm³. 3 The melt index is 2g / 10min and the melting point is 130℃.

[0068] Performance testing:

[0069] Tensile strength: Refer to GB / T 1040.3.

[0070] Elongation at break: Refer to GB / T 1040.3.

[0071] Elastic modulus: Refer to GB / T 1040.3.

[0072] CPP membrane permeation resistance: The CPP membranes of Examples 1-10 and Comparative Examples 1-2 were sealed into small bags of 100mm*100mm size. After sealing three sides, the same weight of electrolyte (e.g., 35g) was poured in, and then the bags were sealed. The bags were weighed and recorded, and the initial value and the weight values ​​(total weight of electrolyte and CPP bag) at different time periods were recorded. The bags were then suspended in the air, and the loss of electrolyte was calculated to determine the permeation of electrolyte in different CPP membranes.

[0073] Table 1. Performance test results of CPP membrane.

[0074]

[0075] As shown in Table 1, the erucic acid amide type slip agent in the core layer of the present invention has little effect on the permeation resistance, tensile strength, elongation at break, and elastic modulus of the CPP membrane.

[0076] Table 2. Performance test results of CPP membrane.

[0077]

[0078] As shown in Tables 1 and 2, the block copolymer polypropylene and high-density polyethylene used in the core layer of the embodiments of the present invention can effectively improve the permeability resistance of the CPP membrane; while the block copolymer polypropylene or high-density polyethylene used in the core layer of Comparative Examples 1 to 2 resulted in a decrease in the permeability resistance of the CPP membrane.

[0079] Depend on Figure 1 and Figure 2 It can be seen that the CPP film obtained in Example 1 has better impact resistance, and the CPP films obtained in Examples 2-5 and Examples 7-10 have similar effects to those in Example 1; while the CPP film obtained in Example 6 has poor impact resistance.

[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 core layer, characterized in that, The first raw material forming the core layer, by weight percentage, comprises: 51-87.8% block copolymer polypropylene, 2-15% high-density polyethylene, and 10-30% polyolefin elastomer; The block copolymerized polypropylene is an ethylene and propylene alternating block copolymer, and the density of the block copolymerized polypropylene is 0.88-0.92 g / cm 3 , the melt index is 1-6 g / 10 min, and the melting point is 150-163℃. The high-density polyethylene has a density of 0.955-0.97 g / cm 3 , a melt index of 6 g / 10 min, and a melting point of 128 °C. The polyolefin elastomer is a copolymer of ethylene, propylene, and the density of the polyolefin elastomer is 0.85 to 0.90 g / cm 3 , the melt index is 5 to 6 g / 10 min, and the melting point is 60 to 100°C.

2. The core layer as described in claim 1, characterized in that, The first raw material also includes 0.2-4% of erucamide-type slip agent.

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

4. The CPP membrane according to claim 3, characterized in that, The second raw material forming the composite layer includes 95-100% by mass of a first homopolypropylene having a density of 0.88-0.93 g / cm 3 and a melt index of 6-14 g / 10 min and a melting point of 160-170°C, and 0-5% by mass of a silica opening agent.

5. The CPP membrane according to claim 3, characterized in that, The third raw material forming the heat-sealing layer, by weight percentage, comprises 58-82% random copolymer polypropylene and 10-30% homopolymer polypropylene. 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 / 10min, and the melting point is 120~140℃; 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℃.

6. The CPP membrane according to claim 5, characterized in that, The third raw material also includes 0.5-6% silica opening agent and 0.5-6% erucamide-type slip agent.

7. The CPP membrane according to any one of claims 3 to 6, characterized in that, The thickness percentages of the heat-sealing layer, the core layer, and the composite layer in the CPP film are 5~25%: 50~90%: 5~25%, and the thickness of the CPP film is 30~100.

8. 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 multi-layer co-extrusion casting technology.

9. An aluminum-plastic film, comprising a CPP film, a PET layer, a nylon layer, and an aluminum foil layer, characterized in that, A nylon layer, an aluminum foil layer, and a CPP film are sequentially stacked on a PET layer, wherein the CPP film is the CPP film according to any one of claims 3 to 7.

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