Aluminum-coated composite film based on polylactic acid interlayer

Abstract

The utility model belongs to packaging material technical field relates to a kind of based on aluminized composite film of polylactic acid interlayer, and the aluminized composite film is composed of the aluminium foil, polylactic acid interlayer and polymer film of laminated arrangement;Among them, the polylactic acid interlayer is completely degraded into carbon dioxide and water in recycling process.The utility model introduces the polylactic acid interlayer of easy degradation between aluminium foil and polymer film, and it is completely degraded into carbon dioxide and water in recycling process, and the separation difficulty and recovery cost of aluminium foil and polymer film are reduced sufficiently.

Description

Technical Field

[0001] This utility model belongs to the field of packaging material technology, and relates to an aluminized composite film, and more particularly to an aluminized composite film based on polylactic acid interlayer, its preparation method, recycling method and application. Background Technology

[0002] Metallized composite film is a high-performance material composed of aluminum foil and polymer film. Due to its excellent barrier properties, heat resistance, and mechanical properties, it has been widely used in food packaging, pharmaceutical packaging, electronic insulation, and many other fields. However, the recycling of this composite material has always been a major challenge for the industry. Because of the significant differences in chemical properties and the tight bond between aluminum foil and polymer film, traditional recycling methods struggle to efficiently separate these two materials, leading to increasing resource waste and environmental pollution.

[0003] Currently, the recycling of aluminized composite membranes mainly includes high-temperature pyrolysis, physical separation, and chemical dissolution. High-temperature pyrolysis involves mechanically crushing the composite membrane and then converting the polymer film into oil and gas, and the aluminum foil into coarse aluminum powder. However, this method has significant drawbacks: the purification of the oil and gas is complex and costly, and the pyrolysis process releases harmful gases, causing secondary pollution. Physical separation separates metallic aluminum and polymer particles by physical crushing and utilizing density or magnetic differences. However, this method has low separation efficiency and is difficult to completely separate, resulting in low purity of the recycled material. Chemical dissolution achieves separation by dissolving the interlayer adhesive with a specialized stripping solution. However, this method has specific requirements for the structure of the composite membrane, and the stripping solution is costly and the process is complex.

[0004] Therefore, how to provide an aluminized composite film and its recycling method to reduce the difficulty of separating aluminum foil and polymer film and the recycling cost has become a technical problem that urgently needs to be solved in this field. Utility Model Content

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an aluminum-plated composite film based on a polylactic acid interlayer. By introducing an easily degradable polylactic acid interlayer between the aluminum foil and the polymer film, the polylactic acid is completely degraded into carbon dioxide and water during the recycling process, which significantly reduces the difficulty of separating the aluminum foil and the polymer film and the recycling cost.

[0006] To achieve the objective of this utility model, the following technical solution is adopted:

[0007] This utility model provides an aluminized composite film based on polylactic acid interlayer, characterized in that the aluminized composite film is composed of aluminum foil, polylactic acid interlayer and polymer film stacked together.

[0008] The polylactic acid interlayer is completely degraded into carbon dioxide and water during the recycling process.

[0009] This invention introduces a biodegradable polylactic acid interlayer between aluminum foil and polymer film, which completely degrades into carbon dioxide and water during the recycling process. This significantly reduces the difficulty of separating aluminum foil and polymer film and the recycling cost. Furthermore, the degradation products do not pollute the environment and meet the requirements of green and environmentally friendly production.

[0010] Preferably, the polylactic acid interlayer is made of any one or a combination of at least two of L-polylactic acid, D-polylactic acid, or racemic polylactic acid.

[0011] Preferably, the polylactic acid in the polylactic acid interlayer has a weight-average molecular weight of 100,000 to 200,000.

[0012] Preferably, the polymer film is made of polyethylene, polypropylene, or polyethylene terephthalate.

[0013] Preferably, the polymer film is modified with maleic anhydride.

[0014] Preferably, the thickness of the aluminum foil is 30-50 μm.

[0015] Preferably, the thickness of the polylactic acid interlayer is 10-12 μm.

[0016] Preferably, the thickness of the polymer film is 30-80 μm.

[0017] In this invention, the preparation method of the above-mentioned polylactic acid interlayer-based aluminized composite film includes any one of the following two methods:

[0018] (A) Two-step coating: Polylactic acid interlayer and polymer film are sequentially coated on the surface of aluminum foil, and the aluminum-plated composite film is obtained after trimming.

[0019] (B) Single-step coating: Polylactic acid interlayer is coated between aluminum foil and polymer film, and the aluminum-coated composite film is obtained after trimming.

[0020] Preferably, the lamination temperature of the polylactic acid interlayer in methods (A) and (B) is 170°C-230°C, respectively.

[0021] Preferably, both method (A) and method (B) involve a cooling process after coating, and the cooling process includes air cooling and / or water cooling.

[0022] Preferably, the polymer film of method (A) is modified by adding maleic anhydride before coating.

[0023] Preferably, the polymer film of method (B) contains maleic anhydride in its material.

[0024] In this invention, the recycling method for the polylactic acid-based aluminized composite membrane includes sequential crushing, industrial composting, and physical separation.

[0025] Preferably, the temperature of the industrial composting is 58℃-60℃, the humidity is 85%-95%, and the time is 3-6 months.

[0026] Preferably, the physical separation method includes any one or a combination of at least two of the following: air blowing, gravity settling, or cyclone separation.

[0027] In this invention, the aforementioned aluminized composite film based on polylactic acid interlayer is used as a packaging material.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention introduces a biodegradable polylactic acid interlayer between aluminum foil and polymer film, which completely degrades into carbon dioxide and water during the recycling process. This significantly reduces the difficulty of separating aluminum foil and polymer film and the recycling cost. Furthermore, the degradation products do not pollute the environment and meet the requirements of green and environmentally friendly production. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the aluminum-plated composite film structure provided by this utility model;

[0031] Figure 2 This is a schematic diagram of the process for preparing an aluminum-coated composite film using a two-step coating method according to this utility model;

[0032] Figure 3 This is a schematic diagram of the process for preparing an aluminum-coated composite film using a single-step coating process according to this utility model.

[0033] Wherein: 1-aluminum foil; 2-polylactic acid interlayer; 3-polymer film; 4-guide roller; 5-pressure roller; 6-traction roller; 7-circular knife. Detailed Implementation

[0034] The technical solution of this utility model will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of this utility model and should not be considered as specific limitations thereof.

[0035] One embodiment of this utility model provides an aluminized composite film based on polylactic acid interlayer, characterized in that the aluminized composite film is composed of aluminum foil, polylactic acid interlayer and polymer film stacked together.

[0036] The polylactic acid interlayer is completely degraded into carbon dioxide and water during the recycling process.

[0037] This invention introduces a biodegradable polylactic acid interlayer between aluminum foil and polymer film, which completely degrades into carbon dioxide and water during the recycling process. This significantly reduces the difficulty of separating aluminum foil and polymer film and the recycling cost. Furthermore, the degradation products do not pollute the environment and meet the requirements of green and environmentally friendly production.

[0038] In some embodiments, the polylactic acid interlayer is made of any one or a combination of at least two of polylactic acid (PLLA), polylactic acid (PDLA), or racemic polylactic acid (PDLLA). Typical but non-limiting combinations include combinations of polylactic acid and PDLA, combinations of PDLA and racemic polylactic acid, combinations of polylactic acid and racemic polylactic acid, or combinations of polylactic acid, PDLA, and racemic polylactic acid.

[0039] The polylactic acid material used in this invention is derived from renewable biomass resources (such as corn, sugarcane, cassava, etc.) and is prepared through processes such as fermentation, saccharification, esterification and polymerization. The production process is pollution-free, and the final degradation products are harmless substances, which is in line with the concept of green environmental protection.

[0040] In some embodiments, the weight-average molecular weight of polylactic acid in the polylactic acid interlayer is 100,000 to 200,000, for example, it can be 100,000, 110,000, 120,000, 130,000, 140,000, 150,000, 160,000, 170,000, 180,000, 190,000 or 200,000, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In some embodiments, the polymer film is made of polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET).

[0042] In some embodiments, the polymer film is modified with maleic anhydride to enhance the polarity of the polymer film and improve the interfacial bonding between the polylactic acid interlayer and the polymer film.

[0043] In some embodiments, the thickness of the aluminum foil is 30-50 μm, for example, it can be 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm or 50 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0044] In some embodiments, the thickness of the polylactic acid interlayer is 10-12 μm, for example, it can be 10 μm, 10.2 μm, 10.4 μm, 10.6 μm, 10.8 μm, 11 μm, 11.2 μm, 11.4 μm, 11.6 μm, 11.8 μm or 12 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0045] In this invention, the thickness of the polylactic acid (PLA) interlayer is crucial for balancing the degradation rate and interfacial adhesion. When the thickness is less than 10 μm, although the PLA interlayer can degrade rapidly during recycling, as an interlayer between the aluminum foil and the polymer film, an excessively thin layer cannot provide sufficient interfacial adhesion during processing, thus failing to ensure good adhesion between the composite film layers and affecting the overall performance of the composite film. When the thickness is greater than 12 μm, an excessively thick PLA interlayer is prone to incomplete degradation during recycling, affecting the separation effect between the aluminum foil and the polymer film, resulting in microplastic contamination and an unnecessary increase in preparation costs.

[0046] In some embodiments, the thickness of the polymer film is 30-80 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm or 80 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0047] In some embodiments, the preparation method of the above-mentioned polylactic acid-based aluminized composite film includes any one of the following two methods:

[0048] (A) Two-step coating: Polylactic acid interlayer and polymer film are sequentially coated on the surface of aluminum foil, and the aluminum-plated composite film is obtained after trimming.

[0049] (B) Single-step coating: Polylactic acid interlayer is coated between aluminum foil and polymer film, and the aluminum-coated composite film is obtained after trimming.

[0050] In some embodiments, the lamination temperature of the polylactic acid interlayer described in methods (A) and (B) is 170°C-230°C, for example, it can be 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C or 230°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0051] Since polylactic acid has a melting point of approximately 157°C and a decomposition temperature of approximately 230°C, this invention specifically limits the coating temperature of the polylactic acid interlayer to 170°C-230°C. This temperature range ensures that the polylactic acid is fully melted and plasticized during the coating process, forming a uniform melt, thereby guaranteeing the uniformity and quality stability of the coating. At the same time, it avoids the decomposition of polylactic acid during the coating process due to excessively high temperatures, preventing the generation of harmful substances and ensuring the biodegradability and environmental performance of polylactic acid.

[0052] In some embodiments, the coating process described in both method (A) and method (B) is followed by a cooling treatment, and the cooling treatment includes air cooling and / or water cooling.

[0053] In some embodiments, the polymer film of method (A) is modified by adding maleic anhydride before coating.

[0054] In some embodiments, the polymer film of method (B) contains maleic anhydride in its material.

[0055] In some embodiments, the above-described recycling method for polylactic acid-based aluminized composite membranes includes sequential crushing, industrial composting, and physical separation.

[0056] In some embodiments, the temperature of the industrial compost is 58°C-60°C, for example, 58°C, 58.5°C, 59°C, 59.5°C or 60°C; the humidity is 85%-95%, for example, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94% or 95%; and the time is 3-6 months, for example, 3 months, 3.5 months, 4 months, 4.5 months, 5 months, 5.5 months or 6 months, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0057] In some embodiments, the physical separation method includes any one or a combination of at least two of the following: air blowing, gravity settling, or cyclone separation. Typical but non-limiting combinations include a combination of air blowing and gravity settling, a combination of gravity settling and cyclone separation, a combination of air blowing and cyclone separation, or a combination of air blowing, gravity settling, and cyclone separation.

[0058] In some embodiments, the above-described polylactic acid-based aluminized composite film is used as a packaging material.

[0059] The numerical range described in this utility model includes not only the point values ​​listed above, but also any point values ​​within the numerical range that are not listed. Due to space limitations and for the sake of brevity, this utility model will not exhaustively list all the specific point values ​​included in the range.

[0060] Example 1

[0061] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method, such as... Figure 1 As shown, the aluminized composite membrane is composed of stacked aluminum foil 1, polylactic acid interlayer 2, and polymer film 3. The polylactic acid interlayer 2 is completely degraded into carbon dioxide and water during the recycling process.

[0062] Specifically, the polylactic acid interlayer 2 is made of L-polylactic acid with a weight-average molecular weight of 150,000; the polymer film 3 is made of polyethylene with a weight-average molecular weight of 100,000, and the polymer film 3 is modified with maleic anhydride. The aluminum foil 1 has a thickness of 40 μm, the polylactic acid interlayer 2 has a thickness of 11 μm, and the polymer film 3 has a thickness of 55 μm.

[0063] This embodiment uses a two-step coating process to prepare the above-mentioned aluminum-coated composite film, such as... Figure 2 As shown, the two-step coating process includes unwinding, PLA coating, PE coating, trimming, and rewinding in sequence. Specifically, after the aluminum foil 1 is unwound, it is coated with polylactic acid interlayer 2 and polymer film 3 in sequence during the conveying process of guide roller 4. During the coating process, it passes through pressure roller 5 and cooling treatment. Then, under the traction of traction roller 6, it passes through the trimming treatment of circular knife 7 and is rewound to obtain aluminized composite film.

[0064] In this embodiment, the coating temperature of the polylactic acid interlayer 2 is 200°C, the coating temperature of the polymer film 3 is 140°C, and the polymer film 3 is modified by adding 5 wt% maleic anhydride before coating. Since the addition method of maleic anhydride has no significant impact on the overall performance of the aluminized composite film, its addition conditions are not specifically described here.

[0065] Example 2

[0066] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method, such as... Figure 1 As shown, the aluminized composite membrane is composed of stacked aluminum foil 1, polylactic acid interlayer 2, and polymer film 3. The polylactic acid interlayer 2 is completely degraded into carbon dioxide and water during the recycling process.

[0067] Specifically, the polylactic acid interlayer 2 is made of dextrorotatory polylactic acid with a weight-average molecular weight of 100,000; the polymer film 3 is made of polyethylene with a weight-average molecular weight of 100,000, and the polymer film 3 is modified with maleic anhydride. The aluminum foil 1 has a thickness of 30 μm, the polylactic acid interlayer 2 has a thickness of 10 μm, and the polymer film 3 has a thickness of 30 μm.

[0068] This embodiment uses a two-step coating process to prepare the above-mentioned aluminum-coated composite film, such as... Figure 2As shown, the two-step coating process includes unwinding, PLA coating, PE coating, trimming, and rewinding in sequence. Specifically, after the aluminum foil 1 is unwound, it is coated with polylactic acid interlayer 2 and polymer film 3 in sequence during the conveying process of guide roller 4. During the coating process, it passes through pressure roller 5 and cooling treatment. Then, under the traction of traction roller 6, it passes through the trimming treatment of circular knife 7 and is rewound to obtain aluminized composite film.

[0069] In this embodiment, the coating temperature of the polylactic acid interlayer 2 is 170°C, the coating temperature of the polymer film 3 is 140°C, and the polymer film 3 is modified by adding 5 wt% maleic anhydride before coating. Since the addition method of maleic anhydride has no significant impact on the overall performance of the aluminized composite film, its addition conditions are not specifically described here.

[0070] Example 3

[0071] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method, such as... Figure 1 As shown, the aluminized composite membrane is composed of stacked aluminum foil 1, polylactic acid interlayer 2, and polymer film 3. The polylactic acid interlayer 2 is completely degraded into carbon dioxide and water during the recycling process.

[0072] Specifically, the polylactic acid interlayer 2 is made of racemic polylactic acid with a weight-average molecular weight of 200,000; the polymer film 3 is made of polyethylene with a weight-average molecular weight of 100,000, and the polymer film 3 is modified with maleic anhydride. The aluminum foil 1 has a thickness of 50 μm, the polylactic acid interlayer 2 has a thickness of 12 μm, and the polymer film 3 has a thickness of 80 μm.

[0073] This embodiment uses a two-step coating process to prepare the above-mentioned aluminum-coated composite film, such as... Figure 2 As shown, the two-step coating process includes unwinding on one side, coating with PLA, coating with PE, trimming, and winding in sequence. Specifically, after the aluminum foil 1 is unwound, it is coated with polylactic acid interlayer 2 and polymer film 3 in sequence during the conveying process of guide roller 4. During the coating process, it passes through pressure roller 5 and cooling treatment. Then, under the traction of traction roller 6, it passes through the trimming treatment of circular knife 7 and is wound up to obtain aluminized composite film.

[0074] In this embodiment, the coating temperature of the polylactic acid interlayer 2 is 230°C, the coating temperature of the polymer film 3 is 140°C, and the polymer film 3 is modified by adding 5 wt% maleic anhydride before coating. Since the addition method of maleic anhydride has no significant impact on the overall performance of the aluminized composite film, its addition conditions are not specifically described here.

[0075] Example 4

[0076] This embodiment provides an aluminized composite film based on polylactic acid interlayer and its preparation method. The structure of the aluminized composite film is the same as that in Embodiment 1, so it will not be described again here.

[0077] The difference lies in that this embodiment uses a single-step coating process to prepare the aforementioned aluminized composite film, such as... Figure 3 As shown, the single-step coating process includes unwinding on both sides, PLA coating, trimming, and winding in sequence. Specifically, after the aluminum foil 1 and the polymer film 3 are unwound simultaneously, a polylactic acid interlayer 2 is coated between the aluminum foil 1 and the polymer film 3 during the conveying process of the guide roller 4. During the coating process, the film passes through the pressure roller 5 and cooling treatment. Then, under the traction of the traction roller 6, the film is trimmed by the circular knife 7 and wound up to obtain the aluminized composite film.

[0078] In this embodiment, the polylactic acid interlayer 2 is coated at a temperature of 200°C, and the polymer film 3 contains 5 wt% maleic anhydride. Since the method of adding maleic anhydride has no significant impact on the overall performance of the aluminized composite film, its addition conditions are not specifically described here.

[0079] Example 5

[0080] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method. Except for changing the material of the polymer film 3 to polypropylene with the same molecular weight, the other structures and conditions are the same as in Example 1, so they will not be described in detail here.

[0081] Example 6

[0082] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method. Except that the material of the polymer film 3 is changed to polyethylene terephthalate with the same molecular weight and its thickness is changed to 35 μm, the rest of the structure and conditions are the same as in Example 1, so they will not be described in detail here.

[0083] Example 7

[0084] This embodiment provides an aluminum-plated composite film based on polylactic acid interlayer and its preparation method. Except for changing the thickness of polylactic acid interlayer 2 to 8μm, the other structures and conditions are the same as in Example 1, so they will not be described in detail here.

[0085] Example 8

[0086] This embodiment provides an aluminum-plated composite film based on polylactic acid interlayer and its preparation method. Except for changing the thickness of polylactic acid interlayer 2 to 14 μm, the other structures and conditions are the same as in Example 1, so they will not be described in detail here.

[0087] Example 9

[0088] This embodiment provides an aluminum-coated composite film based on polylactic acid interlayer and its preparation method. Except for the absence of maleic anhydride modification treatment before coating the polymer film 2, the structure and conditions are the same as in Example 1, so they will not be described in detail here.

[0089] Comparative Example 1

[0090] This comparative example provides an aluminum-coated composite film and its preparation method. Except for replacing the polylactic acid interlayer 2 with a polyethylene adhesive layer of the same thickness, the other structures and conditions are the same as in Example 1, so they will not be described in detail here.

[0091] Performance testing

[0092] The aluminized composite membranes obtained in Examples 1-9 and Comparative Example 1 were subjected to simulated recycling processes, including sequential crushing, industrial composting, and physical separation. Specifically, the aluminized composite membranes were first mechanically crushed into fragments with an average particle size of 2 cm, then industrially composted for 5 months at a temperature of 60°C and a humidity of 90%, and finally separated by air. The separation rate of the aluminized composite membranes was roughly estimated, and the relevant results are shown in Table 1 below.

[0093] Table 1

[0094] Aluminized composite film Separation rate Is there any residual polylactic acid interlayer? Example 1 ≥99％ no Example 2 ≥99％ no Example 3 ≥99％ no Example 4 ≥99％ no Example 5 ≥99％ no Example 6 ≥99％ no Example 7 ≥99％ no Example 8 ≥95％ yes Example 9 ≥99％ no Comparative Example 1 ≤80％ /

[0095] Therefore, this utility model introduces an easily degradable polylactic acid interlayer between the aluminum foil and the polymer film, which is completely degraded into carbon dioxide and water during the recycling process. This significantly reduces the difficulty of separating the aluminum foil and the polymer film and the recycling cost. Moreover, the degradation products do not pollute the environment and meet the requirements of green and environmentally friendly production.

[0096] The above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. An aluminized composite film based on polylactic acid interlayer, characterized in that, The aluminized composite film is composed of stacked aluminum foil, polylactic acid interlayer and polymer film; The polylactic acid interlayer is completely degraded into carbon dioxide and water during the recycling process.

2. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The polylactic acid interlayer is made of any one of L-polylactic acid, D-polylactic acid, or racemic polylactic acid.

3. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The polylactic acid in the polylactic acid interlayer has a weight-average molecular weight of 100,000 to 200,000.

4. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The polymer film is made of materials including polyethylene, polypropylene, or polyethylene terephthalate.

5. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The thickness of the aluminum foil is 30-50 μm.

6. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The thickness of the polylactic acid interlayer is 10-12 μm.

7. The aluminized composite film based on polylactic acid interlayer according to claim 1, characterized in that, The thickness of the polymer film is 30-80 μm.

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