Core layer, CPP film, preparation method of CPP film and aluminum plastic film

Abstract

The invention discloses a core layer, a CPP film, a preparation method thereof and an aluminum plastic film, first raw materials for forming the core layer comprise 51-88% of block co-polypropylene and 2-15% of high density polyethylene, the block co-polypropylene is an ethylene and propylene alternating block copolymer, the density of the block co-polypropylene is 0.88-0.92 g / cm < 3 >, the melt index is 1-6 g / 10 min, the melting point is 150-163 DEG C, the density of the high density polyethylene is 0.955-0.97 g / cm < 3 >, and the melt index of the high density polyethylene is 1-6 g / 10 min. The melting 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] The invention belongs to the field of lithium ion battery packaging materials, and in particular relates to a core layer, a CPP film, a preparation method thereof and an aluminum-plastic film. Background Art

[0002] Aluminum-plastic film is a composite soft packaging shell material used to encapsulate lithium-ion batteries. It is composed of an outer layer of nylon (or PET, etc.), an intermediate aluminum foil, and an inner layer of CPP film compounded by adhesives. This three-layer structure gives the aluminum-plastic film multiple characteristics such as puncture resistance, high barrier properties, electrolyte resistance, high temperature insulation resistance, and high cold stamping formability. Among them, the CPP film, as the inner heat-sealing layer, is not only required to have good heat-sealing adhesion, but also to be able to prevent the leaked electrolyte from corroding the aluminum foil to ensure the safety and stability of the battery. CPP film, or cast polypropylene film, is a non-stretched, non-directional flat extruded film, generally composed of a heat-sealing layer, a core layer, and a composite layer. The core layer of the CPP film is mostly made of homopolymers because homopolymers have excellent rigidity and can meet the film's requirements for support performance. At the same time, the weight of the core layer material accounts for 60% to 70% of the total film weight, which has an important impact on the overall performance of the film.

[0003] As the middle layer in the multi-layer composite film, the core layer mainly bears the important responsibility of providing the film with mechanical properties and supporting functions. However, in the existing technology of multi-layer co-extruded film production, the core layer link 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, but existing materials often cannot meet these requirements at the same time, and a trade-off needs to be made between various properties. Summary of the invention

[0004] In view of the deficiencies of the prior art, the core layer of the present invention is used to prepare a CPP film, and the CPP film has good permeability resistance, impact resistance, tensile strength, elongation at break and elastic modulus.

[0005] The object of the present invention is to provide a core layer, wherein the first raw material forming the core layer comprises, by weight percentage, 51-88% of block copolymer polypropylene and 2-15% of 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 / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , melt index is 6~14g / 10min, melting point is 128~140℃.

[0006] In some embodiments of the present invention, the first raw material further comprises 10-30% of a 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 / cm 3 , the melting point is 60~100℃ and the melting index is 1~6g / 10min.

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

[0008] Another object of the present invention is to provide a CPP film, wherein the CPP film comprises a heat-sealing layer, a core layer and a composite layer which are stacked in sequence.

[0009] In some embodiments of the present invention, the second raw material of the composite layer includes 95-100% of the first homopolypropylene and 0-5% of the silica opening agent, and the density of the first homopolypropylene is 0.88-0.93 g / cm 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 includes 58-82% of random copolymer polypropylene and 10-30% of the second homopolymer polypropylene, in terms of mass percentage, wherein the random copolymer polypropylene is a ternary random copolymer of propylene, ethylene and butene, and the density of the random copolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 4-12 g / 10 min, the melting point is 120-140 ° C; the density of the second homopolymer polypropylene is 0.88-0.93 g / cm 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 also includes 0.5-6% of a silicon dioxide opening agent.

[0012] In some embodiments of the present invention, the third raw material also includes 0.5-6% of erucamide type lubricant.

[0013] In the following embodiment of the present invention, the thickness percentage of the heat sealing layer, the core layer and the composite layer in the CPP film is 5-25%: 50-90%: 5-25%. Specifically, the thickness percentage of the heat sealing layer, the core layer and the composite layer includes but is not limited to 5%: 90%: 5%, 10%: 80%: 10%, 15%: 70%: 15%, 20%: 60%: 20%, 25%: 50%: 25%.

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

[0015] Another object of the present invention is to provide a method for preparing the CPP film, which adopts a multi-layer co-extrusion casting method to form a heat-sealing layer, a core layer and a composite layer which are stacked in sequence.

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

[0017] In some embodiments of the present invention, the aluminum-plastic film further comprises a PET layer, a nylon layer and an aluminum foil layer, and the nylon layer, the aluminum foil layer and the CPP film are sequentially stacked on the PET layer.

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

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

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

[0021] Compared with the prior art, the present invention has the following beneficial effects:

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

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

[0024] (3) The core layer mixed composite layer material used in the present invention enables the prepared CPP film to have good tensile strength, elongation at break and elastic modulus. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the stamping molding effect of the CPP film of Example 1.

[0026] Figure 2 This is the stamping molding effect of the CPP film of Example 4. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0028] The raw materials used in the present invention are all conventionally commercially available.

[0029] Example 1

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

[0031] The raw materials for forming the heat sealing layer are, by weight percentage, 82% random copolymer polypropylene, 10% homopolymer polypropylene, 4% silica anti-blocking agent and 4% erucic acid amide type slip agent, wherein the random copolymer polypropylene is a ternary random copolymer of propylene, ethylene and butene, and the density of the random copolymer polypropylene is 0.88~0.93g / cm 3 , melt index is 4~12g / 10min, melting point is 120~140℃; density of homopolymer polypropylene is 0.88~0.93g / cm 3 , the melting point is 160~170℃;

[0032] The raw materials for forming the core layer are: block copolymer polypropylene 63%, high-density polyethylene 10%, polyolefin elastomer 25% and erucic acid amide type lubricant 2%, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88~0.92g / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , the melt index is 6~14g / 10min, the melting point is 128~140℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85~0.90g / cm 3 , melt index is 1~6g / 10min, melting point is 60~100℃;

[0033] The raw materials for forming the composite layer are: 95% homopolymer polypropylene and 5% silica opening agent, wherein the density of homopolymer polypropylene is 0.88~0.93g / cm 3 , the melting point is 160~170℃;

[0034] According to the percentage by mass, the raw materials of the heat sealing layer, the core layer and the composite layer are melted at high temperature in the screw according to the above required proportions, and put into the three extruders corresponding to the three-layer co-extrusion casting machine, and the thickness percentage of the three layers is set to 15%:70%:15%, and the extrusion temperature of the die head is 180~270℃. Among them, the temperature of the extruder for forming the heat sealing layer is 180~270℃, the extrusion rate is 90~200kg / h, and the temperature of the extruder for forming the core layer is 180~2 70℃, extrusion rate is 400~700kg / h, the extruder temperature for forming the composite layer is 180~260℃, the extrusion rate is 90~200kg / h, the film is cooled and shaped on the smooth roller, the temperature of the smooth roller is 20~60℃, and it is stretched by guide rollers, tempered, corona treated, thickness detected, online defect monitoring, flash, and winding. The production line speed is 50~150m / min, and the winding tension is 5~20kg to obtain a 40μm CPP film.

[0035] Example 2

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

[0037] The difference from Example 1 is that the mass percentage of the raw materials for forming the core layer and the thickness percentage of the three layers are different, and the others are the same as Example 1; in terms of mass percentage, the raw materials for forming the core layer in this embodiment are: 51% block copolymer polypropylene, 15% high-density polyethylene, 30% polyolefin elastomer and 4% erucic acid amide type lubricant, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88~0.92g / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , the melt index is 6~14g / 10min, the melting point is 128~140℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85~0.90g / cm 3 , the melt index is 1~6g / 10min, the melting point is 60~100℃; the thickness percentage of the three layers is set to 5%:90%:5%; and a 50μm CPP film is obtained.

[0038] Example 3

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

[0040] The difference from Example 1 is that the mass percentage of the raw materials for forming the core layer and the thickness percentage of the three layers are different, and the others are the same as Example 1; in terms of mass percentage, the raw materials for forming the core layer in this embodiment are: block copolymer polypropylene 87.8%, high-density polyethylene 2%, polyolefin elastomer 10% and erucic acid amide type lubricant 0.2%, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88~0.92g / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , the melt index is 6~14g / 10min, the melting point is 128~140℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85~0.90g / cm 3 , the melt index is 1~6g / 10min, the melting point is 60~100℃; the thickness percentage of the three layers is set to 25%:50%:25%; and a 45μm CPP film is obtained.

[0041] Example 4

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

[0043] The difference from Example 1 is that the raw materials for forming the core layer are different, and the rest are the same as Example 1; in terms of mass percentage, the raw materials for forming the core layer in this embodiment are: 63% block copolymer polypropylene, 10% high-density polyethylene, 25% polyolefin elastomer and 2% erucic acid amide type lubricant, 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 / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , the melt index is 6~14g / 10min, the melting point is 128~140℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.86~0.9g / cm 3 , the melting point is 55~95℃.

[0044] Example 5

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

[0046] The difference from Example 1 is that the raw materials for forming the core layer are different, and the rest are the same as Example 1; in terms of mass percentage, the raw materials for forming the core layer in this embodiment are: 65% block copolymer polypropylene, 10% high-density polyethylene and 25% polyolefin elastomer, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88~0.92g / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , the melt index is 6~14g / 10min, the melting point is 128~140℃; the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85~0.90g / cm 3 , the melting point is 60~100℃ and the melting index is 1~6g / 10min.

[0047] Example 6

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

[0049] The difference from Example 1 is that the raw materials for forming the composite layer are different, and the rest are the same as Example 1; in terms of mass percentage, the raw materials for forming the composite layer in this embodiment are: 95% homopolypropylene and 5% silica opening agent, wherein the density of homopolypropylene is 0.89-0.92 g / cm 3 , the melting point is 158~166℃.

[0050] Example 7

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

[0052] The difference from Example 1 is that the raw materials for forming the composite layer are different, and the rest are the same as Example 1; in terms of mass percentage, the raw materials for forming the composite layer in this embodiment are: 100% homopolypropylene, wherein the density of the homopolypropylene is 0.88-0.93 g / cm 3 , the melt index is 6~14g / 10min, and the melting point is 160~170℃.

[0053] Example 8

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

[0055] The difference from Example 1 is that the raw material random copolymer polypropylene for forming the heat seal layer is different. The other aspects are the same as Example 1. The raw material random copolymer polypropylene for forming the heat seal layer in this embodiment is a copolymer of ethylene and propylene, and the density of the random copolymer polypropylene is 0.86~0.9g / cm 3, melt index is 5~13g / 10min, melting point is 125~145℃.

[0056] Example 9

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

[0058] The difference from Example 1 is that the raw material homopolypropylene for forming the heat seal layer is different. The other aspects are the same as Example 1. The density of the raw material homopolypropylene for forming the heat seal layer in this embodiment is 0.89-0.92 g / cm 3 , the melting point is 155~168℃.

[0059] Example 10

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

[0061] The difference from Example 1 is that the raw materials for forming the heat sealing layer are different, and the rest are the same as Example 1; in terms of mass percentage, the raw materials for forming the heat sealing layer in this embodiment are: 72% random copolymer polypropylene and 28% homopolymer polypropylene, wherein the random copolymer polypropylene is a ternary random copolymer of propylene, ethylene and butene, and the density of the random copolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 4~12g / 10min, the melting point is 120~140℃; the density of homopolymer polypropylene is 0.88~0.93g / cm 3 , the melt index is 6~14g / 10min, and the melting point is 160~170℃.

[0062] Comparative Example 1

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

[0064] The difference from Example 1 is that the structure of the raw material block copolymer polypropylene forming the core layer is different. The other aspects are the same as Example 1. The raw material block copolymer polypropylene forming the core layer of this comparative example is ethylene and propylene copolymer, and the density of the block copolymer polypropylene is 0.9~0.92g / cm 3 , the melting point is 145~160℃.

[0065] Comparative Example 2

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

[0067] The difference from Example 1 is that the raw material high-density polyethylene for forming the core layer is different. The other aspects are the same as Example 1. The density of the raw material high-density polyethylene for forming the core layer of this comparative example is 0.957~0.97g / cm 3, the melting point is 130~140℃.

[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 penetration resistance: The CPP films of Examples 1-10 and Comparative Examples 1-2 were respectively sealed into small bags of 100mm*100mm in size. After the three sides were sealed, the same weight of electrolyte, such as 35g, was poured into the bags. The bags were then sealed and the initial value and the weight values ​​(total weight of the electrolyte and the CPP bag) at different subsequent time periods were weighed and recorded. The bags were suspended in the air to calculate the loss of the electrolyte and to determine the penetration of the electrolyte in different CPP films.

[0073] Table 1. CPP film performance test results.

[0074]

[0075] It can be seen from Table 1 that the erucic acid amide type lubricant of the core layer of the present invention has little effect on the permeation resistance of the CPP film, the tensile strength of the CPP film, the elongation at break of the CPP film, and the elastic modulus of the CPP film.

[0076] Table 2. CPP film performance test results.

[0077]

[0078] It can be seen from Table 1 and Table 2 that the block copolymer polypropylene and high-density polyethylene used in the core layer of the present invention can effectively improve the permeability resistance of the CPP film; while the block copolymer polypropylene or high-density polyethylene used in the core layer of Comparative Examples 1-2 causes the permeability resistance of the CPP film to decrease.

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

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that after reading the specification of this application, the technicians can still modify or replace the specific implementation mode of the present invention with equivalents, but these modifications or changes do not deviate from the scope of protection of the pending claims of the present application.

Claims

1. A core layer, characterized in that: In terms of mass percentage, the first raw material for forming the core layer includes: 51-88% of block copolymer polypropylene and 2-15% of 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 / cm 3 , the melt index is 1~6g / 10min, the melting point is 150~163℃; the density of the high-density polyethylene is 0.955~0.97g / cm 3 , melt index is 6~14g / 10min, melting point is 128~140℃.

2. The core layer according to claim 1, characterized in that The first raw material also includes 10-30% of polyolefin elastomer, the polyolefin elastomer is a copolymer of ethylene and propylene, and the density of the polyolefin elastomer is 0.85-0.90 g / cm 3 , the melting point is 60~100℃ and the melting index is 1~6g / 10min.

3. The core layer according to claim 1, characterized in that The first raw material also includes 0.2-4% of erucamide type lubricant.

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

5. The CPP film according to claim 4, characterized in that: In terms of mass percentage, the second raw material of the composite layer includes 95-100% of the first homopolypropylene and 0-5% of the silica opening agent, and the density of the first homopolypropylene is 0.88-0.93 g / cm 3 , the melt index is 6~14g / 10min, and the melting point is 160~170℃.

6. The CPP film according to claim 4, characterized in that In terms of mass percentage, the third raw material of the heat-sealing layer includes 58-82% of random copolymer polypropylene and 10-30% of the second homopolymer polypropylene, wherein the random copolymer polypropylene is a ternary random copolymer of propylene, ethylene and butene, and the density of the random copolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 4-12 g / 10 min, the melting point is 120-140 ° C; the density of the second homopolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 6~14g / 10min, and the melting point is 160~170℃.

7. The CPP film according to claim 6, characterized in that The third raw material also includes 0.5-6% of a silica opening agent and 0.5-6% of an erucamide type lubricant.

8. The CPP film according to any one of claims 4 to 7, 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 um.

9. A method for preparing a CPP film according to claim 4 to 7, characterized in that: A multi-layer co-extrusion casting method is adopted to form a heat-sealing layer, a core layer and a composite layer which are stacked in sequence.

10. 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 laminated on the PET layer. The CPP film is the CPP film according to any one of claims 4 to 8.

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