CPP film and preparation method and application thereof

Abstract

The invention discloses a CPP film, which comprises a heat sealing layer and a composite layer, and the heat sealing layer is prepared from the following first raw materials in percentage by mass: 58-82% of polypropylene random copolymer and 10-30% of homo-polypropylene; and a second raw material for forming the composite layer comprises 95-100% of homo-polypropylene and 0-5% of a silicon dioxide anti-blocking agent. The CPP film obtained by the invention has good peel strength, light transmittance and haze, and has a uniform whitening effect after one-sealing and two-sealing.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion battery packaging materials, and in particular relates to a CPP film and a preparation method and application thereof. Background Art

[0002] CPP film, namely cast polypropylene film, is a non-stretched, non-directional flat extruded film produced by melt saliva quenching, with the characteristics of fast production speed, high output, uniform film thickness, excellent transparency and glossiness. There are two ways to produce CPP film: single-layer cast film and multi-layer co-extrusion cast film. The multi-layer co-extrusion cast film can generally be divided into three layers: heat sealing layer, composite layer and core layer.

[0003] In the production process of CPP film, the compounding of heat-sealing layer and composite layer is a key link, but there are also some technical problems. However, due to the difference in material properties and various factors in the processing process, poor bonding sometimes occurs, resulting in leakage or delamination of the package during use. In addition, the material selection of heat-sealing layer and composite layer needs to take into account multiple performance requirements, such as peel strength, light transmittance, haze, and uniform whitening effect of one seal and two seals. However, existing materials often find it difficult to take into account multiple performance requirements at the same time. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention solves the composite problem of the heat-sealing layer and the composite layer in the prior art, and the obtained CPP film has good peel strength, light transmittance and haze, and a uniform whitening effect of one seal and two seals.

[0005] The object of the present invention is to provide a CPP film, the CPP film comprises a heat-sealing layer and a composite layer, and the first raw material forming the heat-sealing layer comprises, by weight percentage, 58-82% of random copolymerized polypropylene and 10-30% of a first homopolymerized polypropylene, the random copolymerized polypropylene is a ternary random copolymer of propylene, ethylene and butene, and the density of the random copolymerized 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 first homopolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 6-14 g / 10 min, and the melting point is 160-170° C. The second raw material for forming the composite layer includes: 95-100% of the second homopolymer polypropylene and 0-5% of the silica opening agent, and 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℃.

[0006] In some embodiments of the present invention, the first raw material further includes 0.5-6% of a silicon dioxide opening agent.

[0007] In some embodiments of the present invention, the first raw material further includes 0.5-6% of erucamide type lubricant.

[0008] In some embodiments of the present invention, the CPP film further comprises a core layer, and the third raw material for forming the core layer comprises: 51-88% block copolymer polypropylene and 2-15% high-density polyethylene, wherein the block copolymer polypropylene is an alternating block copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.88-0.92 g / 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℃.

[0009] In some embodiments of the present invention, the third 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.

[0010] In some embodiments of the present invention, the third raw material also includes 0.2-4% erucamide type lubricant.

[0011] In some embodiments 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%.

[0012] Another object of the present invention is to provide a method for preparing a CPP film, comprising the following steps:

[0013] S1. The raw materials of the heat sealing layer, the core layer and the composite layer are put into three extruders corresponding to the three-layer co-extrusion casting machine, extruded through the die head to obtain a hot melt film;

[0014] S2. The hot melt film is cooled and shaped into a film on a smooth roller;

[0015] S3. The cooled and shaped film is stretched by guide rollers, subjected to tempering treatment, corona treatment, thickness detection, online defect monitoring, flashing, and winding to obtain a CPP film.

[0016] In some embodiments of the present invention, in S1, the temperature of extrusion through the die is 180-270°C.

[0017] In some embodiments of the present invention, in S2, the temperature of the smooth roller is 20-60°C.

[0018] Another object of the present invention is to provide an aluminum-plastic film, comprising a CPP film, a PET layer, a nylon layer and an aluminum foil layer, wherein the nylon layer, the aluminum foil layer and the CPP film are sequentially stacked on the PET layer, the CPP film is the CPP film according to any one of claims 1 to 6, the thickness of the PET layer is 10 to 14 um, the thickness of the nylon layer is 20 to 30 um, and the thickness of the aluminum foil layer is 40 to 50 um.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The CPP film of the invention has good peeling strength, light transmittance and haze, and has a uniform whitening effect of one seal and two seals. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the whitening effect of a sealed CPP film in Example 1.

[0022] Figure 2 This is the double seal whitening effect of the CPP film of Example 1.

[0023] Figure 3 This is the whitening effect of one seal of the CPP film of Comparative Example 1.

[0024] Figure 4 This is the whitening effect of the second seal of the CPP film of Comparative Example 1. DETAILED DESCRIPTION

[0025] 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.

[0026] Example 1

[0027] This embodiment provides a CPP film, and the specific process is as follows:

[0028] 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 , 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 melting point is 160~170℃;

[0029] 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℃;

[0030] 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℃;

[0031] 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.

[0032] Example 2

[0033] This embodiment provides a CPP film, and the specific process is as follows:

[0034] The difference from Example 1 is that the mass percentage of the raw materials for forming the heat-sealing layer and the raw materials for the composite 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 heat-sealing layer in this embodiment are: 58% random copolymer polypropylene, 30% homopolymer polypropylene, 6% silica opening agent and 6% erucic acid amide type lubricant, 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 , 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°C; the raw material for forming the composite layer is: 100% homopolymer polypropylene, the density of the homopolymer polypropylene is 0.88-0.93g / cm 3 , the melt index is 6~14g / 10min, the melting point is 160~170℃; the thickness percentage of the three layers is set to 5%:90%:5%; and a 50μm CPP film is obtained.

[0035] Example 3

[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 heat-sealing layer and the raw materials for the composite 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 heat-sealing layer in this embodiment are: 74% random copolymer polypropylene, 25% homopolymer polypropylene, 0.5% silica opening agent and 0.5% erucic acid amide type lubricant, 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 , melt index is 4~12g / 10min, melting point is 120~140℃; density of homopolymer polypropylene is 0.88~0.93g / cm 3 The melt index is 6-14 g / 10 min, and the melting point is 160-170 ° C. The raw materials for forming the composite layer are: 97% homopolymer polypropylene and 3% silica opening agent, and the density of the homopolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 6~14g / 10min, the melting point is 160~170℃; the thickness percentage of the three layers is set to 25%:50%:25%; and a 45μm CPP film is obtained.

[0038] Example 4

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

[0040] 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 , melt index is 4~12g / 10min, melting point is 120~140℃; 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℃.

[0041] Example 5

[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: 51% block copolymer polypropylene, 15% high-density polyethylene, 30% polyolefin elastomer and 4% erucic acid amide type lubricant, wherein the block copolymer polypropylene is a copolymer of ethylene and propylene, and the density of the block copolymer polypropylene is 0.9-0.92 g / cm 3 , the melt index is 3-9 g / 10 min, the melting point is 145-160 ° C; the density of the high-density polyethylene is 0.955-0.97 g / 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.

[0044] Example 6

[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: 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 0.957~0.97g / cm 3, the melt index is 2~9g / 10min, the melting point is 130~140℃; 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 7

[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 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℃.

[0050] Example 8

[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 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.

[0053] Comparative Example 1

[0054] This comparative example 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 comparative example 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] Comparative Example 2

[0057] This comparative example 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 comparative example is 0.89-0.92 g / cm 3 , the melting point is 155~168℃.

[0059] Comparative Example 3

[0060] This comparative example 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 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 comparative example are: 95% homopolypropylene and 5% silica opening agent, wherein the density of the homopolypropylene is 0.89-0.92 g / cm 3 , the melting point is 158~166℃.

[0062] Performance Test:

[0063] The first seal refers to direct sealing at the sealing point after compounding, without the need to apply electrolyte, while the second seal refers to applying electrolyte at the sealing point and then heat sealing.

[0064] The aluminum-plastic film is a PET layer, a nylon layer, an aluminum foil layer and an aluminum-plastic film obtained by sequentially laminating the CPP films of Examples 1 to 8 or Comparative Examples 1 to 3, wherein the thickness of the PET layer is 12 um, the thickness of the nylon layer is 25 um, and the thickness of the aluminum foil layer is 45 um.

[0065] Light transmittance: refer to GB / T 2410.

[0066] Haze: Refer to GB / T 2410.

[0067] Peel strength between CPP film and aluminum foil layer: GB / T 10004-2008.

[0068] Table 1. CPP film performance test results.

[0069]

[0070] As can be seen from Table 1, the silica opening agent and erucic acid amide type lubricant raw materials of the heat seal layer of the present invention have little effect on the peel strength, light transmittance and haze between the CPP film and the aluminum foil layer; the polyolefin elastomer and erucic acid amide type lubricant of the core layer also have little effect on the peel strength, light transmittance and haze between the CPP film and the aluminum foil layer.

[0071] Table 2. CPP film performance test results.

[0072]

[0073] As can be seen from Table 2, the homopolymer polypropylene raw material of the heat sealing layer of the present invention has little effect on the peel strength between the CPP film and the aluminum foil layer, and the raw material CPP film used for the heat sealing layer and the core layer of the present invention has good peel strength, light transmittance and haze; the heat sealing layer of Comparative Example 1 adopts random copolymer polypropylene with different structures, and the light transmittance and haze of the prepared CPP film decrease, and the peel strength between the CPP film and the aluminum foil layer decreases slightly; the heat sealing of Comparative Example 2 adopts homopolymer polypropylene with different structures, and the peel strength between the prepared CPP film and the aluminum foil layer decreases slightly; the composite layer of Comparative Example 3 adopts homopolymer polypropylene with different structures, and the peel strength, light transmittance and haze performance of the prepared CPP film and the aluminum foil layer all decrease.

[0074] Depend on Figure 1 and Figure 2 It can be seen that after the two surfaces of the CPP film obtained in Example 1 are peeled off, there is still a thin film on the surface protecting the aluminum foil, and there is no aluminum leakage. It can be judged that the electrolyte does not pass through the CPP film into the aluminum foil layer, and then corrode the aluminum foil. Whether it is one seal or two seals, they are uniformly whitened. The CPP films obtained in Examples 2 to 8 have similar effects to those in Example 1; while after the two surfaces of the CPP film obtained in Comparative Example 1 are peeled off, the film at the sealing portion is broken, and the sealing whitening effect is poor.

[0075] 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 CPP film comprising a heat sealing layer and a composite layer, characterized in that: In terms of mass percentage, the first raw material forming the heat seal layer includes: 58-82% of random copolymer polypropylene and 10-30% of first 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 first homopolymer polypropylene is 0.88-0.93 g / cm 3 , the melt index is 6-14 g / 10 min, and the melting point is 160-170° C. The second raw material for forming the composite layer includes: 95-100% of the second homopolymer polypropylene and 0-5% of the silica opening agent, and 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℃.

2. The CPP film according to claim 1, characterized in that The first raw material also includes 0.5-6% of a silicon dioxide opening agent.

3. The CPP film according to claim 1, characterized in that The first raw material also includes 0.5-6% of erucamide type lubricant.

4. The CPP film according to claim 1, characterized in that The CPP film also includes a core layer, and the third raw material for forming the core layer includes: 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 / 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℃.

5. The CPP film according to claim 4, characterized in that The third raw material also includes 10-30% of 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.

6. The CPP film according to claim 4, characterized in that The third raw material also includes 0.2-4% of erucamide type lubricant.

7. A method for preparing the CPP film according to claims 4 to 6, characterized in that: The following steps are involved: S1. The raw materials of the heat sealing layer, the core layer and the composite layer are put into three extruders corresponding to the three-layer co-extrusion casting machine, extruded through the die head to obtain a hot melt film; S2. The hot melt film is cooled and shaped into a film on a smooth roller; S3. The cooled and shaped film is stretched by guide rollers, subjected to tempering treatment, corona treatment, thickness detection, online defect monitoring, flashing, and winding to obtain a CPP film.

8. The preparation method according to claim 7, characterized in that: In S1, the temperature of extrusion through the die head is 180-270°C.

9. The preparation method according to claim 7, characterized in that: In S2, the temperature of the smooth roller is 20-60°C.

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 stacked on the PET layer, wherein the CPP film is the CPP film according to any one of claims 1 to 6, the thickness of the PET layer is 10 to 14 um, the thickness of the nylon layer is 20 to 30 um, and the thickness of the aluminum foil layer is 40 to 50 um.

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