Medium-resistant flexible package composite film and preparation process thereof

Abstract

The invention relates to the technical field of flexible package composite films, and discloses a medium-resistant flexible package composite film and a preparation process thereof.The structure of the composite film sequentially comprises a nylon layer, an aluminum foil layer and a modified polypropylene layer, and the modified polypropylene layer is prepared from polypropylene, medium-resistant filler and an initiator; the medium-resistant filler is prepared by carrying out surface modification on nano silicon dioxide by utilizing a medium-resistant modifier, on one hand, the medium-resistant modifier enhances the interfacial interaction force between the nano silicon dioxide and a polypropylene matrix, improves the compatibility and enhances the mechanical property of polypropylene; on the other hand, through chemical crosslinking between the medium-resistant filler and the polypropylene, the compactness of the polypropylene is improved, and the physical barrier effect of the nano silicon dioxide is utilized, so that a barrier effect can be generated on a medium, the medium is difficult to enter a gap between two phases, and the medium-resistant performance of the polypropylene is enhanced. The flexible package composite film is prepared through dry-method compounding and can be used for packaging lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of flexible packaging composite film technology, and in particular to a media-resistant flexible packaging composite film and its preparation process. Background Technology

[0002] Currently, lithium battery flexible packaging composite films consist of, from the outside in, a nylon (PA) or polyethylene terephthalate (PET) layer, a barrier aluminum foil layer, a polypropylene layer, and an adhesive. The outer layer of the lithium battery flexible packaging composite film serves as a protective layer, requiring excellent impact resistance, puncture resistance, abrasion resistance, heat resistance, and insulation. The barrier aluminum foil layer provides shaping and barrier functions, preventing moisture penetration and external damage to the battery's interior. The polypropylene layer, as the inner layer, directly contacts the organic electrolyte of the lithium battery and needs excellent mechanical properties and resistance to dielectrics. While pure polypropylene, under prolonged contact with the electrolyte, typically does not undergo significant chemical dissolution or molecular chain breakage, the solvent components in the electrolyte may cause polypropylene to swell. This swelling weakens the intermolecular forces, leading to a decrease in the mechanical properties of the polypropylene. Summary of the Invention

[0003] This invention proposes a media-resistant flexible packaging composite film and its preparation process. By preparing a modified polypropylene layer with excellent media resistance and mechanical properties as the inner layer film, the flexible packaging composite film is prepared by dry lamination with a nylon layer and an aluminum foil layer, which can be used to package lithium batteries.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A media-resistant flexible packaging composite film, wherein the structure of the composite film is, in sequence, a nylon layer / an aluminum foil layer / a modified polypropylene layer;

[0006] The modified polypropylene layer comprises the following raw materials in parts by weight:

[0007] 80-100 parts polypropylene;

[0008] 6-10 parts of media-resistant filler;

[0009] 0.3-0.8 parts initiator;

[0010] Among them, the media-resistant filler is prepared by surface modification of nano-silica using a media-resistant modifier.

[0011] Furthermore, the preparation method of the media-resistant modifier is as follows:

[0012] Under the action of a catalyst, 1 molar equivalent of 4,4-dihydroxybiphenyl reacts with 2 molar equivalents of 3-chloropropanol in a substitution reaction to give dihydroxybiphenyl ether.

[0013] Under the action of p-toluenesulfonic acid, 1 molar equivalent of dihydroxydiphenyl ether and 1 molar equivalent of oleoyl chloride undergo esterification to obtain a media-resistant modifier.

[0014] Furthermore, the catalyst is potassium carbonate or sodium carbonate.

[0015] A process for preparing a media-resistant flexible packaging composite film includes the following steps:

[0016] Step 1: Mix polypropylene, media-resistant filler and initiator evenly, add to twin-screw extruder, melt graft, extrude and granulate to obtain modified polypropylene masterbatch, add modified polypropylene masterbatch to single-screw extrusion blown film mill, blow mold to form film to obtain modified polypropylene layer;

[0017] Step 2: Prepare a flexible packaging composite film by dry lamination of nylon layer / aluminum foil layer / modified polypropylene layer.

[0018] Furthermore, the initiator is dicumyl peroxide or di-tert-butyl peroxide.

[0019] Furthermore, the screw temperature of the twin-screw extruder is 180-200℃.

[0020] Furthermore, the dielectric-resistant flexible packaging composite film is used for packaging lithium batteries.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention prepares a media-resistant modifier, which is then used to surface-modify nano-silica to obtain a media-resistant filler. This filler is added to polypropylene, where it chemically crosslinks with the polypropylene under the action of an initiator, resulting in modified polypropylene. On one hand, the media-resistant modifier enhances the interfacial interaction between the nano-silica and the polypropylene matrix, improving compatibility and strengthening the mechanical properties of the polypropylene. On the other hand, the chemical crosslinking of the media-resistant filler with the polypropylene increases the density of the polypropylene, and the physical barrier effect of the nano-silica prevents the media from easily entering the gap between the two phases. Experimental results show that the modified polypropylene prepared by this invention exhibits excellent media resistance and mechanical properties.

[0023] This invention prepares a flexible packaging composite film by dry lamination of a nylon layer, an aluminum foil layer, and a modified polypropylene layer, which can be used for packaging lithium batteries. Detailed Implementation

[0024] Experimental Example 1:

[0025] The method for preparing media-resistant fillers is as follows:

[0026] In the presence of potassium carbonate, 1 molar equivalent of 4,4-dihydroxybiphenyl reacts with 2 molar equivalents of 3-chloropropanol in a substitution reaction to give dihydroxybiphenyl ether.

[0027] Under the action of p-toluenesulfonic acid, 1 molar equivalent of dihydroxydiphenyl ether and 1 molar equivalent of oleoyl chloride undergo esterification to obtain a media-resistant modifier.

[0028] A medium-resistant filler was obtained by surface modification of nano-silica using a medium-resistant modifier.

[0029] The specific steps for preparing media-resistant fillers are as follows:

[0030] Step 1: Add 1.9g of 4,4-dihydroxybiphenyl to 20mL of toluene, mix well, then add 1.9g of 3-chloropropanol and 0.3g of potassium carbonate, purge with nitrogen for protection, stir and reflux for 6h, cool to room temperature, add water, stir, filter, wash, and dry to obtain dihydroxybiphenyl ether.

[0031] Step 2: Add 3g of dihydroxydiphenyl ether and 0.1g of p-toluenesulfonic acid to 20mL of xylene, stir and mix evenly, then slowly add 3g of oleoyl chloride. After the addition is complete, heat to 75℃, keep warm and stir for 4h, cool to room temperature, neutralize, wash with water, put in an ice bath at -5℃, filter, collect crystals, wash, dry, and obtain the media-resistant modifier.

[0032] The chemical structural formula of the media resistance modifier is:

[0033] ;

[0034] The 1H NMR characterization results of the media-resistant modifier are as follows: 1 H NMR (400MHz, DMSO-D6, δ, ppm): 0.88-0.90 (m, 3H), 1.26-1.32 (m, 20H), 1.56-1.63 (m, 2H), 1.97-2.04 (m, 6H), 2.13-2.19 (m, 2H), 2. 29-2.32(t, 2H), 2.87-2.89(t, 1H), 3.70-3.74(m, 2H), 4.09-4.19(m, 6H), 5.30-5.36(m, 2H), 6.97-7.00(d, 4H), 7.59-7.61(d, 4H);

[0035] Step 3: Add 3g of media-resistant modifier to 10mL of N,N-dimethylformamide, stir and mix for 10min, add 0.7g of nano silica (particle size 10μm), sonicate and mix for 10min, heat to 70℃, stir and react for 12h, centrifuge, wash, and dry to obtain media-resistant filler.

[0036] Example 1:

[0037] A media-resistant flexible packaging composite film, wherein the structure of the flexible packaging composite film is, in sequence, a nylon layer / an aluminum foil layer / a modified polypropylene layer;

[0038] The modified polypropylene layer comprises the following raw materials in parts by weight:

[0039] 100 parts of polypropylene (brand name F401);

[0040] Six portions of media-resistant packing material (prepared in Experimental Example 1);

[0041] 0.5 parts dicumyl peroxide;

[0042] A process for preparing a media-resistant flexible packaging composite film includes the following steps:

[0043] Step 1: Mix polypropylene, media-resistant filler, and dicumyl peroxide evenly, and add it to a twin-screw extruder. The screw temperature is 190℃ and the screw speed is 50r / min. Melt grafting is performed, followed by extrusion granulation to obtain modified polypropylene masterbatch. The modified polypropylene masterbatch is then added to a single-screw extrusion blown film mill and blown into a film. The barrel temperature is 200℃ in zone 1, 195℃ in zone 2, 190℃ in zone 3, and 185℃ in zone 4 to obtain a modified polypropylene layer with a thickness of 45μm.

[0044] Step 2: Prepare a flexible packaging composite film by dry lamination of nylon layer / aluminum foil layer / modified polypropylene layer, wherein the thickness of nylon layer is 25μm and the thickness of aluminum foil layer is 40μm.

[0045] Example 2:

[0046] A media-resistant flexible packaging composite film, wherein the structure of the flexible packaging composite film is, in sequence, a nylon layer / an aluminum foil layer / a modified polypropylene layer;

[0047] The modified polypropylene layer comprises the following raw materials in parts by weight:

[0048] 100 parts of polypropylene (brand name F401);

[0049] Eight portions of media-resistant packing material (prepared in Experimental Example 1);

[0050] 0.5 parts dicumyl peroxide;

[0051] A process for preparing a media-resistant flexible packaging composite film includes the following steps:

[0052] Step 1: Mix polypropylene, media-resistant filler, and dicumyl peroxide evenly, and add it to a twin-screw extruder. The screw temperature is 190℃ and the screw speed is 50r / min. Melt grafting is performed, followed by extrusion granulation to obtain modified polypropylene masterbatch. The modified polypropylene masterbatch is then added to a single-screw extrusion blown film mill and blown into a film. The barrel temperature is 200℃ in zone 1, 195℃ in zone 2, 190℃ in zone 3, and 185℃ in zone 4 to obtain a modified polypropylene layer with a thickness of 45μm.

[0053] Step 2: Prepare a flexible packaging composite film by dry lamination of nylon layer / aluminum foil layer / modified polypropylene layer, wherein the thickness of nylon layer is 25μm and the thickness of aluminum foil layer is 40μm.

[0054] Example 3:

[0055] A media-resistant flexible packaging composite film, wherein the structure of the flexible packaging composite film is, in sequence, a nylon layer / an aluminum foil layer / a modified polypropylene layer;

[0056] The modified polypropylene layer comprises the following raw materials in parts by weight:

[0057] 100 parts of polypropylene (brand name F401);

[0058] 10 portions of media-resistant packing material (prepared in Experimental Example 1);

[0059] 0.5 parts dicumyl peroxide;

[0060] A process for preparing a media-resistant flexible packaging composite film includes the following steps:

[0061] Step 1: Mix polypropylene, media-resistant filler, and dicumyl peroxide evenly, and add it to a twin-screw extruder. The screw temperature is 190℃ and the screw speed is 50r / min. Melt grafting is performed, followed by extrusion granulation to obtain modified polypropylene masterbatch. The modified polypropylene masterbatch is then added to a single-screw extrusion blown film mill and blown into a film. The barrel temperature is 200℃ in zone 1, 195℃ in zone 2, 190℃ in zone 3, and 185℃ in zone 4 to obtain a modified polypropylene layer with a thickness of 45μm.

[0062] Step 2: Prepare a flexible packaging composite film by dry lamination of nylon layer / aluminum foil layer / modified polypropylene layer, wherein the thickness of nylon layer is 25μm and the thickness of aluminum foil layer is 40μm.

[0063] Comparative Example 1:

[0064] A flexible packaging composite film, the structure of which consists of a nylon layer / aluminum foil layer / modified polypropylene layer in sequence;

[0065] The polypropylene layer comprises the following parts by weight of raw materials:

[0066] 100 parts of polypropylene (brand name F401);

[0067] A process for preparing a flexible packaging composite film includes the following steps:

[0068] Step 1: Add polypropylene to a single-screw extruder and blown film, blown into a film. The barrel temperature is 200℃ in zone 1, 195℃ in zone 2, 190℃ in zone 3, and 185℃ in zone 4 to obtain a polypropylene layer with a thickness of 45μm.

[0069] Step 2: Prepare a flexible packaging composite film by dry lamination of nylon layer / aluminum foil layer / polypropylene layer, wherein the thickness of nylon layer is 25μm and the thickness of aluminum foil layer is 40μm.

[0070] Performance testing:

[0071] I. Testing of Media Resistance

[0072] The modified polypropylene masterbatch from Examples 1-3 and Comparative Example 1 was used to prepare test strips that met the test specifications. According to the test method for mass change in standard GB / T 11547-2008 "Resistance of Plastics to Liquid Chemical Reagents", the test strips were added to ethylene carbonate at a soaking temperature of 70°C for one week. The mass change of the test strips was recorded, and the test results are shown in Table 1.

[0073] Table 1 Test results of media resistance

[0074] serial number Quality change rate (%) Example 1 0.036 Example 2 0.028 Example 3 0.031 Comparative Example 1 0.51

[0075] As shown in Table 1, the modified polypropylene prepared in the embodiments of the present invention has excellent resistance to media.

[0076] II. Mechanical Property Testing

[0077] The test specimens from Examples 1-3 and Comparative Example 1 were immersed in ethylene carbonate at a temperature of 90°C for 36 hours. The tensile strength of the specimens before and after immersion was tested according to the test conditions in standard GB / T 1040.3-2006 "Determination of Tensile Properties of Plastics - Part 3 Test Conditions for Films and Sheets". The tensile rate was 5 mm / min. The results are shown in Table 2.

[0078] Table 2 Test results of mechanical properties

[0079] serial number Tensile strength (MPa) before immersion Tensile strength (MPa) after immersion Example 1 34.8 32.8 Example 2 36.2 34.4 Example 3 35.4 33.5 Comparative Example 1 31.2 23.1

Claims

1. A media resistant flexible pouch composite film characterized by, The structure of the composite film is nylon layer / aluminum foil layer / modified polypropylene layer in sequence. The modified polypropylene layer comprises the following raw materials by weight: 80-100 parts of polypropylene; 6-10 parts of medium-resistant filler; 0.3-0.8 parts of initiator; The medium-resistant filler is prepared by surface modification of nano-silicon dioxide with a medium-resistant modifier; The chemical structural formula of the medium-resistant modifier is: 。 2. The medium resistant flexible pouch composite film according to claim 1, characterized in that, The preparation method of the medium-resistant modifier is: Under the action of a catalyst, 1 mole equivalent of 4,4-dihydroxydiphenyl is subjected to substitution reaction with 2 mole equivalents of 3-chloropropanol to obtain dihydroxydiphenyl ether; Under the action of p-toluenesulfonic acid, 1 mole equivalent of dihydroxydiphenyl ether is subjected to esterification reaction with 1 mole equivalent of oleoyl chloride to obtain the medium-resistant modifier.

3. The medium resistant flexible pouch composite film according to claim 2, wherein, The catalyst is potassium carbonate or sodium carbonate.

4. The process for the production of a media resistant flexible pouch composite film according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Step one: uniformly mix polypropylene, medium-resistant filler and initiator, add them into a twin-screw extruder, melt graft, extrude and granulate to obtain modified polypropylene masterbatch, add the modified polypropylene masterbatch into a single-screw extrusion film blowing machine, blow into a film to obtain a modified polypropylene layer; Step two: prepare the soft packaging composite film by dry compounding the nylon layer / aluminum foil layer / modified polypropylene layer.

5. The medium resistant flexible pouch composite film according to claim 1, wherein, The initiator is dicumyl peroxide or di-tert-butyl peroxide.

6. The process for preparing a medium resistant flexible pouch composite film according to claim 4, wherein, The screw temperature of the twin-screw extruder is 180-200 DEG C.

7. The medium resistant flexible pouch composite film according to claim 1, wherein, The medium-resistant soft packaging composite film is used for packaging lithium batteries.

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