An aluminum-foil-free dual barrier layer composite film

Abstract

The utility model discloses a kind of aluminium foil-free double barrier layer composite film, including aluminium foil-free double barrier layer composite film, the aluminium foil-free double barrier layer composite film includes surface layer and bottom layer, and surface layer and bottom layer are connected by interlayer adhesion, the surface layer is constituted by PET base film and alumina sol-gel coating layer, the interlayer is environmental protection type polyurethane adhesive, the bottom layer is constituted by CPP base film and vacuum evaporation aluminium layer, the utility model is by adopting PET base film and the alumina sol-gel coating layer of plasma strengthening treatment constitutes surface layer, PET base film provides excellent mechanical properties to resist processing tension pull, the continuous dense barrier film of ultra-thin alumina coating layer is formed, and the surface layer is synergic, has tensile resistance, processing-resistant characteristic, can also efficiently intercept external water vapor, realizes the primary accurate barrier function to water vapor.

Description

Technical Field

[0001] This utility model mainly relates to the field of composite film technology, specifically to a composite film with a double barrier layer without aluminum foil. Background Technology

[0002] In fields such as food preservation, pharmaceutical protection, and precision electronic component packaging, high-barrier composite films are core packaging materials that ensure the quality and performance stability of the contents. They need to effectively block the penetration of small molecules such as oxygen, water vapor, and volatile substances to achieve the core requirements of extending the shelf life of food, maintaining the active ingredients of pharmaceuticals, and preventing electronic components from being affected by moisture and oxidation.

[0003] However, in practical applications, composite films have gradually revealed their shortcomings in line with the industry's development trends of environmental protection, low cost, and multi-functionality: First, the compatibility between aluminum foil and plastic base film is very different, making it difficult to separate individual components after lamination using conventional physical or chemical methods. After disposal, they mostly rely on incineration or landfill. Incineration can easily cause furnace corrosion, while landfill poses environmental risks due to the difficulty in degrading aluminum foil. Second, aluminum foil has high procurement costs, and composite films containing aluminum foil require multiple processing steps, increasing energy consumption by 25% and extending the production cycle by 40%. At the same time, aluminum foil has poor flexibility and weak impact resistance, making it prone to creases, pinholes, or cracks during processing and transportation, further increasing production costs. Third, the opacity of aluminum foil cannot meet the packaging requirements of baked goods, fresh pre-prepared dishes, etc., which require displaying the contents. Furthermore, it is prone to micro-cracks in low-temperature (such as -18℃ quick-freezing) or repeated folding scenarios, and its barrier performance decreases by 30%-50% with the number of uses, limiting its application scenarios. Utility Model Content

[0004] This utility model provides a solution that is significantly different from existing technologies, addressing the problem that existing solutions are too simplistic. It mainly provides an aluminum foil-free double-barrier composite film to solve the technical problems mentioned in the background.

[0005] The technical solution adopted by this utility model to solve the above-mentioned technical problems is as follows: A foil-free double barrier layer composite film includes a foil-free double barrier layer composite film, which includes a surface layer and a bottom layer, and the surface layer and the bottom layer are bonded together by an intermediate layer. The surface layer is composed of a PET base film and an alumina sol-gel coating layer. The intermediate layer is an environmentally friendly polyurethane adhesive. The bottom layer is composed of a CPP base film and a vacuum-deposited aluminum layer.

[0006] Preferably, the thickness of the PET base film is 10-14 μm.

[0007] Preferably, the alumina sol-gel coating layer has a thickness of ≤50nm and has undergone plasma strengthening treatment.

[0008] Preferably, the thickness of the intermediate layer of environmentally friendly polyurethane adhesive is ≤3μm.

[0009] Preferably, the thickness of the CPP base film is 30-35 μm.

[0010] Preferably, the thickness of the vacuum-deposited aluminum layer is ≤40nm and the aluminum content is <0.1g / m².

[0011] Preferably, the surface layer and the bottom layer adopt a gradient barrier design to achieve a synergistic effect of dual barriers.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows: (1) By using a PET base film and an alumina sol-gel coating layer that has been plasma-enhanced to form the surface layer, the PET base film provides excellent mechanical properties to resist the stretching of the processing tension, and the ultra-thin alumina coating layer forms a continuous and dense barrier film. The two work together to make the surface layer not only have tensile and processing resistance properties, but also intercept external water vapor, thus achieving the primary and precise barrier function against water vapor.

[0013] (2) The bottom layer uses CPP base film and ultra-thin vacuum evaporated aluminum layer. CPP base film provides sufficient mechanical support to resist heat sealing pressure and slight puncture and extrusion. It also has stable heat sealing characteristics to meet sealing requirements. The evaporated aluminum layer has a dense atomic arrangement, which can preferentially and efficiently block oxygen to form a secondary comprehensive barrier. Moreover, the aluminum content is extremely low and there is no solid aluminum foil. After the composite film is discarded, it can be decomposed at high temperature to achieve efficient separation and recycling of the base film and aluminum, solving the environmental pain point of traditional aluminum foil composite films being difficult to recycle.

[0014] The present invention will be explained in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 1 ; Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention. Figure 2 .

[0016] Numbering on the map: 1. Surface layer; 11. PET base film; 12. Alumina sol-gel coating layer; 2. Bottom layer; 21. CPP base film; 22. Vacuum evaporated aluminum layer; 3. Intermediate layer; 100. Aluminum foil-free double barrier layer composite film. Detailed Implementation

[0017] To facilitate understanding of this utility model, a more comprehensive description of the utility model will be given below with reference to the accompanying drawings, which show several embodiments of the utility model. However, the utility model can be implemented in different forms and is not limited to the embodiments described in the text. On the contrary, these embodiments are provided to make the disclosure of the utility model more thorough and comprehensive.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly associated with those skilled in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Please refer to the appendix carefully. Figure 1-2 A foil-free double barrier layer composite film, the foil-free double barrier layer composite film 100 includes a surface layer 1, the surface layer 1 is composed of a PET base film 11 and an alumina sol-gel coating layer 12, the thickness of the PET base film 11 is 12μm, the thickness of the alumina sol-gel coating layer 12 is ≤50nm, and it has been subjected to plasma strengthening treatment.

[0021] The PET base film 11 is made of food-grade biaxially oriented polyethylene terephthalate (PET), with a thickness precisely controlled at 12μm. This thickness design is based on the characteristics of the PET material itself and the application requirements of the composite film: On the one hand, the biaxial stretching process gives the 12μm PET base film 11 excellent mechanical properties, with a longitudinal tensile strength ≥250MPa and a transverse tensile strength ≥230MPa, which can withstand the tensile tension during the composite film processing. On the other hand, the 12μm thickness ensures support while taking into account the overall lightweight requirements of the composite film, and will not reduce the flexibility of the composite film due to excessive thickness of the base film, making it suitable for packaging folding, heat sealing and other processing scenarios.

[0022] The ultrathin thickness of the alumina sol-gel coating layer 12 is the key to balancing barrier performance and structural stability. If the thickness is too thick (>50nm), internal stress is easily generated inside the coating, which may cause cracking and peeling when the PET base film 11 is bent, thus destroying the barrier integrity. A thickness of ≤50nm can form a continuous and dense alumina film layer with no obvious pores and can expand and contract synchronously with the slight deformation of the PET base film 11, thus ensuring structural stability.

[0023] The PET base film 11 and the alumina sol-gel coating layer 12 form a synergistic relationship of rigid support and flexible bonding. The mechanical strength of the PET base film 11 provides a stable carrier for the ultra-thin coating, preventing the coating from being damaged by external forces. The ultra-thin characteristics of the coating and the high adhesion after plasma treatment ensure that it will not affect the flexibility of the PET base film 11. The combination of the two gives the surface layer 1 both tensile strength and processing resistance.

[0024] The top layer 1 and the bottom layer 2 are bonded together by an intermediate layer 3, which is an environmentally friendly polyurethane adhesive. This environmentally friendly polyurethane adhesive uses a single-component solvent-modified polyurethane system, with the core raw materials being polybutylene adipate (PBA) soft segments and isophorone diisocyanate (IPDI) hard segments, supplemented by environmentally friendly ester solvents. No heavy metals, formaldehyde, or phthalate plasticizers are added throughout the process. The thickness of the environmentally friendly polyurethane adhesive in the intermediate layer 3 is ≤3μm. This thickness is strictly controlled to ≤3μm, a parameter designed based on dual considerations: firstly, the 3μm thickness ensures that the adhesive adheres to the top layer... The alumina coating surface of the PET base film 11 and the vapor-deposited aluminum layer surface of the CPP base film 21 form a continuous and uniform film, which covers the tiny pits that may exist on the substrate surface, such as the nanoscale defects of the vapor-deposited aluminum layer, and avoids interlayer delamination due to incomplete adhesive coverage. On the other hand, the ultra-thin thickness of ≤3μm can minimize the impact on the overall flexibility of the composite film. When the composite film is bent, an excessively thick adhesive layer is prone to internal stress, which can cause dead folds or delamination of the film. However, a thickness of 3μm can keep the composite film in good bending performance, making it suitable for actual use scenarios such as packaging folding and heat sealing.

[0025] The bottom layer 2 consists of a CPP base film 21 and a vacuum-deposited aluminum layer 22. The thickness of the CPP base film 21 is 35μm, and the thickness of the vacuum-deposited aluminum layer 22 is ≤40nm. The aluminum content is <0.1g / m². Since the aluminum content is <0.1g / m² and there is no solid aluminum foil structure, the CPP base film and aluminum can be efficiently separated by high-temperature pyrolysis at 400-500℃ after the composite film is discarded. The aluminum powder can be recycled for use as raw material for evaporation, which meets the requirements of environmental protection policies and solves the pain point of traditional aluminum foil composite films being difficult to recycle.

[0026] CPP base film 21 is made of highly crystalline cast polypropylene. Its 35μm thickness design ensures sufficient mechanical support, with a longitudinal tensile strength ≥200MPa and a transverse tensile strength ≥180MPa. It can withstand the heat sealing pressure during packaging processing and minor punctures and compressions during use, preventing damage to the bottom layer 2. It also has heat sealing characteristics suitable for packaging bag making. Its heat sealing temperature range is stable at 120-140℃, and its heat sealing strength is ≥30N / 25mm, which can meet the sealing and leak-proof requirements of frozen foods, capsule medicines and other scenarios.

[0027] The top layer 1 and the bottom layer 2 adopt a gradient barrier design. The moisture permeability of the top layer 1 is <0.5 g / (m².24h) and the oxygen permeability is <1.0 g / (m².24h). The moisture permeability of the bottom layer 2 is <1.0 g / (m².24h) and the oxygen permeability is <30 g / (m².24h). After the composite, the moisture permeability and oxygen permeability are both <0.5 g / (m².24h), realizing the synergistic effect of the double barrier.

[0028] After plasma strengthening, the alumina sol-gel coating layer 12 of the surface layer 1 forms a dense polar oxide layer structure. This structure has a strong adsorption capacity for polar water molecules and can preferentially intercept 70%-80% of external water vapor through physical adsorption and molecular sieving, becoming a primary and precise barrier against water vapor. The vacuum-deposited aluminum layer 22 of the bottom layer 2 is a dense metal film layer with closely packed atoms. Its diffusion resistance to non-polar oxygen molecules is much higher than that of the alumina coating. It can preferentially block 80%-85% of oxygen through the metal lattice barrier, becoming a secondary comprehensive barrier against oxygen. The two layers work together to address the different molecular polarities and permeability characteristics of water vapor and oxygen, avoiding the limitation of a single barrier layer being inefficient in addressing both types of substances. This creates a synergy from the perspective of substance type.

[0029] The present invention has been described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvement made by adopting the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, shall be within the protection scope of the present invention.

Claims

1. A foil-free double-barrier composite film, comprising a foil-free double-barrier composite film (100), characterized in that: The aluminum foil-free double barrier layer composite film (100) includes a top layer (1) and a bottom layer (2), and the top layer (1) and the bottom layer (2) are bonded together by an intermediate layer (3). The top layer (1) is composed of a PET base film (11) and an alumina sol-gel coating layer (12). The intermediate layer (3) is an environmentally friendly polyurethane adhesive. The bottom layer (2) is composed of a CPP base film (21) and a vacuum-deposited aluminum layer (22).

2. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The thickness of the PET base film (11) is 10-14 μm.

3. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The alumina sol-gel coating (12) has a thickness of ≤50nm and is subjected to plasma strengthening treatment.

4. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The thickness of the intermediate layer (3) environmentally friendly polyurethane adhesive is ≤3μm.

5. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The thickness of the CPP base film (21) is 30-35 μm.

6. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The thickness of the vacuum-deposited aluminum layer (22) is ≤40nm, and the aluminum content is <0.1g / m².

7. The aluminum foil-free double-barrier composite film according to claim 1, characterized in that: The surface layer (1) and the bottom layer (2) adopt a gradient barrier design to achieve a synergistic effect of dual barriers.

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