A high-barrier polypropylene film and a method for preparing the same

Abstract

This invention discloses a high-barrier polypropylene film and its preparation method. The high-barrier polypropylene material is composed of the following components by weight: 85-95 parts polypropylene, 1-3.5 parts graphene, 0.3-1.5 parts silane coupling agent, 0.3-0.5 parts long-chain alkylamine, 2-5 parts toughening agent, 0.2-0.5 parts antioxidant, and 0.2-0.4 parts lubricant. The high-barrier polypropylene film provided by this invention not only possesses excellent tensile strength but also excellent barrier properties. Applied in the packaging field, it effectively protects the quality and freshness of food and other products. It can also be used in other agricultural, construction, and medical fields.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-barrier polypropylene film and its preparation method. Background Technology

[0002] Polypropylene film is the most widely used and consumed type of plastic film. Its raw materials are abundant, inexpensive, have low density, are easy to process, and possess excellent overall performance, making it widely used in the rapid packaging industry for food, pharmaceuticals, and cosmetics. However, substances such as oxygen, carbon dioxide, water vapor, and small organic molecules can easily permeate the packaging film, seriously affecting the quality and lifespan of the packaged goods. Therefore, it is necessary to improve the barrier properties of polypropylene film to meet the increasing demands for quality.

[0003] Currently, traditional single-material packaging cannot meet people's requirements for barrier performance. Existing barrier packaging films mainly include composite packaging films and multilayer co-extruded films. Composite films bond different functional film materials together with adhesives, while co-extruded films fuse two or more materials together in a molten state within a single die. CN202411177659.4 discloses an ultra-high barrier homogeneous composite packaging film, which, from the outside in, consists of a substrate layer, an ink layer, a barrier layer, and a heat-sealing layer. The substrate layer is a BOPP film, the ink layer is a water-based ink, the barrier layer is a VMBOPP film, and the heat-sealing layer is a PE composite film. However, composite films are usually composed of multiple films of different materials, making recycling difficult, the process complex, requiring the processing and lamination of multiple layers of films, and demanding strict control of factors such as temperature and humidity, resulting in high production costs. CN202411072119.X discloses a multilayer co-extruded barrier film and its preparation method. The barrier film is composed of an outer layer, a second outer layer, a middle layer, a second inner layer and an inner layer arranged sequentially from the outside to the inside. The barrier film is prepared by blowing the film simultaneously using a five-layer co-extrusion blown film machine. The production process of the multilayer co-extruded film is complex and requires high-precision equipment and technical support, which increases the production cost and operation difficulty.

[0004] In addition to barrier properties, polypropylene film has certain requirements for tensile strength. On industrial production lines, the packaging process often involves high-speed movement and impact. If the tear strength of the packaging film is insufficient, it can easily lead to product damage and leakage.

[0005] Therefore, it is necessary to propose a film material with high barrier properties and excellent tensile strength to effectively solve the problem of poor barrier properties of traditional polypropylene single-material films and improve the tensile strength of the material. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a high-barrier polypropylene film and its preparation method. The prepared polypropylene film not only has high barrier properties but also excellent tensile strength.

[0007] To achieve the above objectives, the present invention provides a high-barrier polypropylene film and a method for preparing it.

[0008] A high-barrier polypropylene material, characterized in that it is prepared from the following components in parts by weight:

[0009] Polypropylene: 85-95 parts

[0010] Graphene: 1-3.5 parts

[0011] Silane coupling agent: 0.3-1.5 parts

[0012] Long-chain alkylamines: 0.3-0.5 parts

[0013] Toughening agent: 2-5 parts

[0014] Antioxidant: 0.2-0.5 parts

[0015] Lubricant: 0.2-0.4 parts

[0016] The long-chain alkylamine is at least one of dodecylamine, hexadecylamine, and octadecylamine.

[0017] The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

[0018] The ratio of the silane coupling agent to the long-chain alkylamine is 1:1 to 3:1.

[0019] The graphene has an aspect ratio of 1000:1 to 6200:1, and preferably, the graphene has an aspect ratio of 2000:1 to 4000:1.

[0020] The toughening agent is at least one of methyl methacrylate-butadiene-styrene terpolymer, ethylene propylene diene monomer (EPDM) rubber, and ethylene-vinyl acetate copolymer.

[0021] The antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant DLTP.

[0022] The lubricant is at least one of calcium stearate, zinc stearate, ethylene bis-stearamide, and polyethylene wax.

[0023] A method for preparing a high-barrier polypropylene film, characterized by comprising the following steps:

[0024] S1: Weigh according to the proportion, first put the long-chain alkylamine, silane coupling agent and graphene into the high-speed mixer and mix for 5-10 minutes at a speed of 500-600 r / min; then add polypropylene, toughening agent, antioxidant and lubricant, mix for 5-10 minutes at a speed of 600-1000 r / min.

[0025] S2: The components of S1, when mixed uniformly, are co-extruded, cooled, and pelletized using a twin-screw extruder to obtain a high-barrier polypropylene material. The process parameters are: Zone 1 170-210℃, Zone 2 200-230℃, Zone 3 200-230℃, Zone 4 200-240℃, Zone 5 200-240℃, Zone 6 200-240℃, and die head temperature 200-240℃. The screw speed is 260-350 rpm.

[0026] S3: The granules obtained in step S2 are blown, stretched, or biaxially stretched to obtain a polypropylene film with high barrier properties.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention uses a compound of dodecylamine and silane coupling agent. The silane coupling agent and dodecylamine work together to chemically bond with the surface groups of graphene sheets, thereby improving the bonding force between the graphene sheets and the matrix material. At the same time, the long-chain structure of the long-chain alkylamine causes the graphene sheets to produce a corresponding steric hindrance effect, which inhibits agglomeration. The two have a synergistic effect, which solves the problem of graphene being easy to agglomerate and difficult to disperse, thereby reducing the water vapor permeation and oxygen permeation of the composite material, improving the barrier performance of the membrane, and at the same time improving the tensile strength of the membrane.

[0029] (2) The present invention adopts a two-step method. First, the silane coupling agent, long-chain alkylamine group and graphene are mixed together, and then the coupling agent is fully contacted with the graphene to improve the dispersion performance of graphene sheets in the matrix. Detailed Implementation

[0030] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, unless otherwise specified, methods not specifically describing conditions or steps are conventional methods, and the reagents and materials used are commercially available. Some raw material information is as follows:

[0032] Polypropylene: Grade PP-PPH-F03D, Suzhou Gaotong New Material Technology Co., Ltd.

[0033] Graphene: Model A120, Suzhou Gaotong New Materials Technology Co., Ltd.

[0034] Other auxiliary materials are standard commercially available products.

[0035] Performance testing:

[0036] The high-performance barrier polypropylene films of the examples and comparative examples were subjected to relevant performance tests according to the following methods:

[0037] (1) Water vapor transmission rate: Tested in accordance with GB / T1037-2021 "Determination of water vapor transmission performance of plastic films and sheets".

[0038] (2) Oxygen permeability: Tested in accordance with GB / T1038.1-2022 "Test method for gas permeability of plastic films and sheets".

[0039] (3) Tensile strength: Tested in accordance with GB / T1040.3-2006, with a film width of 15mm, long strip sample, and a tensile speed of 200mm / min.

[0040] Example 1

[0041] Take 0.3 parts of γ-aminopropyltriethoxysilane, 0.3 parts of dodecylamine, and 1 part of graphene (diameter-to-thickness ratio 1000:1), and mix them in a high-speed mixer for 5 minutes at a speed of 600 r / min. Then add 95 parts of PP, 3 parts of methyl methacrylate-butadiene-styrene terpolymer, 0.2 parts of antioxidant 1010, 0.1 parts of antioxidant 168, and 0.4 parts of calcium stearate, and mix for 5 minutes at a speed of 1000 r / min.

[0042] The uniformly mixed components are co-extruded, cooled, and pelletized using a twin-screw extruder to obtain high-performance barrier polypropylene granules. The process parameters are: zone 1 170℃, zone 2 200℃, zone 3 200℃, zone 4 200℃, zone 5 200℃, zone 6 230℃, and die head temperature 240℃. The screw speed is 260 rpm.

[0043] High-barrier polypropylene granules are melted in a twin-screw extruder, extruded through a die, blow-molded, cooled, and wound to produce a high-barrier polypropylene film. The film thickness is 50 μm.

[0044] Comparative Example 1

[0045] Same as Example 1, except that it does not contain dodecylamine.

[0046] Comparative Example 2

[0047] Same as Example 1, except that it does not contain γ-aminopropyltriethoxysilane (KH550).

[0048] Comparative Example 3

[0049] Same as Example 1, except that it does not contain γ-aminopropyltriethoxysilane (KH550) or dodecylamine.

[0050] Comparative Example 4

[0051] Same as Example 1, except that it does not contain graphene.

[0052] Comparative Example 5

[0053] Same as Example 1, except that it contains 0.1 parts of γ-aminopropyltriethoxysilane (KH550) and 0.5 parts of dodecylamine.

[0054] Table 1. Components and amounts (parts by weight) of the high-barrier polypropylene films in Example 1 and Comparative Examples 1-5.

[0055]

[0056]

[0057] Table 2 Performance tests of high-barrier polypropylene films in Examples 1 and Comparative Examples 1-5

[0058]

[0059] The test results in Table 2 show that the combination of dodecylamine and silane coupling agent has a synergistic effect, solving the problem of graphene's tendency to agglomerate and be difficult to disperse. This reduces the water vapor and oxygen permeation of the composite material, improves the membrane's barrier properties, and simultaneously enhances its tensile strength. The polypropylene membrane showed a 52% reduction in water vapor permeation and a 65.6% reduction in oxygen permeation.

[0060] Example 2

[0061] Take 1.5 parts of γ-glycidyl etheroxypropyltrimethoxysilane (KH560), 0.5 parts of dodecylamine, and 3.5 parts of graphene (diameter-to-thickness ratio 2000:1), and mix them in a high-speed mixer for 10 minutes at a speed of 600 r / min. Then add 85 parts of PP, 2 parts of EPDM rubber, 0.5 parts of antioxidant DLTP, and 0.2 parts of zinc stearate, and mix for 10 minutes at a speed of 600 r / min.

[0062] The uniformly mixed components are co-extruded, cooled, and pelletized using a twin-screw extruder to obtain high-performance barrier polypropylene granules. The process parameters are: zone 1 200℃, zone 2 210℃, zone 3 220℃, zone 4 220℃, zone 5 230℃, zone 6 240℃, and die head temperature 240℃. The screw speed is 350 rpm.

[0063] High-performance barrier polypropylene granules are melted in a twin-screw extruder, formed into thin sheets through a die, and then biaxially stretched to prepare a high-barrier polypropylene film. The film thickness is 30 μm.

[0064] Comparative Example 6

[0065] Same as Example 1, except that the graphene aspect ratio is 500:1.

[0066] Comparative Example 7

[0067] Same as Example 1, except that the graphene aspect ratio is 8000:1.

[0068] Example 3

[0069] Same as Example 1, except that the graphene aspect ratio is 3000:1.

[0070] Example 4

[0071] Same as Example 1, except that the graphene aspect ratio is 4000:1.

[0072] Example 5

[0073] Same as Example 1, except that the graphene aspect ratio is 6200:1.

[0074] Table 3. Components and amounts (parts by weight) of the high-barrier polypropylene films of Examples 2-5 and Comparative Examples 6-7.

[0075]

[0076]

[0077] Table 4 Performance Tests of High Barrier Polypropylene Films in Examples 2-5 and Comparative Examples 6-7

[0078]

[0079] The test results in Table 4 show that the aspect ratio of graphene affects the barrier properties and tensile strength of the film. When the graphene sheets are uniformly distributed in the film, a suitable aspect ratio is conducive to the formation of a complex barrier network, which can achieve a better barrier effect. If the aspect ratio is too small, a barrier network cannot be formed, and if the aspect ratio is too large, the tensile strength of the material will be reduced.

[0080] Example 6

[0081] Take 1 part of γ-methacryloxypropyltrimethoxysilane (KH570), 0.5 parts of octadecylamine, and 2 parts of graphene (aspect ratio 3000:1), and mix them in a high-speed mixer for 5 minutes at a speed of 600 r / min. Then add 90 parts of PP, 3 parts of ethylene-vinyl acetate copolymer, 0.2 parts of antioxidant 1076, 0.2 parts of antioxidant 168, and 0.3 parts of ethylene bis-stearamide, and mix for 5 minutes at a speed of 800 r / min.

[0082] The uniformly mixed components are co-extruded, cooled, and pelletized using a twin-screw extruder to obtain high-barrier polypropylene granules. The process parameters are: zone 1 210℃, zone 2 230℃, zone 3 230℃, zone 4 230℃, zone 5 230℃, zone 6 230℃, die head temperature 240℃, and screw speed 260 rpm.

[0083] High-barrier polypropylene granules are melted in a twin-screw extruder, extruded through a die, blow-molded, cooled, and wound to produce a high-barrier polypropylene film. The film thickness is 15 μm.

[0084] Comparative Example 8

[0085] Same as Example 6, except that: γ-methacryloyloxypropyltrimethoxysilane (KH570), octadecylamine, 2 parts of graphene (diameter-to-thickness ratio 3000:1), PP, ethylene-vinyl acetate copolymer, antioxidant, antioxidant 168, and ethylene bis-stearamide are all added together to a high-speed mixer and mixed for 10 minutes.

[0086] Table 5 Performance tests of high-barrier polypropylene films in Examples 6 and Comparative Example 7

[0087]

[0088] The test results in Table 2 show that mixing silane coupling agent, long-chain alkylamine group and graphene before adding other main and auxiliary materials during the preparation process can improve the dispersion performance of graphene sheets and enhance the barrier properties and tensile strength of the material.

[0089] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0090] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high-barrier polypropylene material, characterized in that, It consists of the following components by weight: Polypropylene: 85-95 parts Graphene: 1-3.5 parts Silane coupling agent: 0.3-1.5 parts Long-chain alkylamines: 0.3-0.5 parts Toughening agent: 2-5 parts Antioxidant: 0.2-0.5 parts Lubricant: 0.2-0.4 parts.

2. The high-barrier polypropylene material according to claim 1, characterized in that, The long-chain alkylamine is at least one of dodecylamine, hexadecylamine, and octadecylamine.

3. The high-barrier polypropylene material according to claim 1, characterized in that, The silane coupling agent is at least one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane.

4. The high-barrier polypropylene material according to claim 1, characterized in that, The ratio of the silane coupling agent to the long-chain alkylamine is 1:1 to 3:

1.

5. The high-barrier polypropylene material according to claim 1, characterized in that: The aspect ratio of the graphene is 1000:1 to 6200:

1.

6. The high-barrier polypropylene material according to claim 1, characterized in that, The toughening agent is at least one of methyl methacrylate-butadiene-styrene terpolymer, ethylene propylene diene monomer (EPDM) rubber, and ethylene-vinyl acetate copolymer.

7. The high-barrier polypropylene material according to claim 1, characterized in that, The antioxidant is at least one of antioxidant 1010, antioxidant 168, antioxidant 1076, and antioxidant DLTP.

8. The high-barrier polypropylene material according to claim 1, characterized in that, The lubricant is at least one of calcium stearate, zinc stearate, ethylene bis-stearamide, and polyethylene wax.

9. A method for preparing a high-barrier polypropylene film, characterized in that, Includes the following steps: S1: Weigh the ingredients according to the specified proportions. First, place the long-chain alkylamine, silane coupling agent, and graphene into a high-speed mixer and mix for 5-10 minutes at a speed of 500-600 rpm. Then, add the polypropylene, toughening agent, antioxidant, and lubricant, and mix for another 5-10 minutes at a speed of 600-1000 rpm. S2: The components of S1, when mixed uniformly, are co-extruded, cooled, and pelletized using a twin-screw extruder to obtain a high-barrier polypropylene material. The process parameters are: Zone 1 170-210℃, Zone 2 200-230℃, Zone 3 200-230℃, Zone 4 200-240℃, Zone 5 200-240℃, Zone 6 200-240℃, and die head temperature 200-240℃. The screw speed is 260-350 rpm. S3: The granules obtained in step S2 are blown, stretched, or biaxially stretched to obtain a polypropylene film with high barrier properties.

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