A PET vacuum metallized composite film and its preparation method

Abstract

This invention discloses a PET vacuum metallized composite film, comprising, from the outside to the inside, a PET substrate layer, an interface modification layer, a gradient metallized layer, a barrier reinforcement layer, an adhesive layer, and a heat-sealing layer. The invention also proposes a method for preparing the PET vacuum metallized composite film, comprising the following steps: S1, PET substrate pretreatment; S2, interface modification layer preparation; S3, gradient metallization layer preparation; S4, barrier reinforcement layer preparation; S5, bonding the adhesive layer and heat-sealing layer; S6, post-treatment. This invention provides a PET vacuum metallized composite film and its preparation method. By optimizing the layered structure, formulation of each layer, and preparation process of the composite film, it achieves a synergistic improvement in the film's barrier properties, flexibility, high-temperature resistance, and adhesion. Simultaneously, it simplifies the process, improves product qualification rate, and meets the requirements for high-temperature retort packaging and long shelf-life packaging.

Description

Technical Field

[0001] This invention relates to the field of packaging materials technology, and in particular to a PET vacuum metallized composite film and its preparation method. Background Technology

[0002] PET vacuum metallized composite film is widely used in packaging for food, pharmaceuticals, and daily necessities due to its advantages such as lightweight, high gloss, and lower cost than aluminum foil composite film. However, existing PET vacuum metallized composite films still have many shortcomings in practical applications: First, the PET substrate has low surface tension and weak interfacial bonding with the metallized layer, making the aluminum layer prone to peeling and detachment, affecting the overall stability of the composite film; Second, traditional metallized layers are prepared using a single vacuum evaporation process, resulting in uniform aluminum grain size, making it difficult to balance flexibility and barrier properties. Repeated bending can easily lead to cracking and a large number of pinholes, resulting in poor oxygen and water barrier performance, failing to meet the packaging requirements of long-shelf-life products; Third, the adhesive has insufficient high-temperature resistance, easily softening and delaminating under high-temperature cooking conditions, and some solvent-based adhesives pose environmental pollution problems; Fourth, the heat-sealing layer has poor cooking resistance, easily deforming at high temperatures, resulting in insufficient heat-sealing strength and affecting the sealing of the packaging; Fifth, inaccurate parameter control in the preparation process leads to poor uniformity of aluminum layer thickness, tension imbalance, low product qualification rate, and difficulty in achieving large-scale industrial production.

[0003] To address the aforementioned issues, various improvement schemes have been proposed in the prior art, such as corona treatment on the PET substrate surface to increase surface tension, or adding a coupling agent coating between the aluminum layer and the substrate. However, the interface modification effect of a single coupling agent coating is limited and still cannot completely solve the problem of aluminum layer detachment. Some schemes employ composite metallization processes, but they do not design a gradient for the aluminum grain size, resulting in a poor balance between flexibility and barrier properties. Other schemes optimize the binder formulation, but their high-temperature resistance and environmental friendliness still need improvement. Therefore, developing a PET vacuum metallized composite film with strong barrier properties, high aluminum layer adhesion, resistance to boiling, good flexibility, and a stable and environmentally friendly preparation process has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a PET vacuum metallized composite film with strong barrier properties, high aluminum layer adhesion, resistance to retorting, and good flexibility, as well as its preparation method. By optimizing the layered structure of the composite film, the formulation of each layer, and the preparation process, the barrier properties, flexibility, high temperature resistance, and adhesion of the composite film are synergistically improved. At the same time, the process is simplified, the product qualification rate is improved, and the needs of high-temperature retorting and long shelf-life packaging are met.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer, an interface modification layer, a gradient metallized layer, a barrier reinforcement layer, an adhesive layer, and a heat-sealing layer.

[0007] The PET substrate layer is a biaxially oriented PET film with a thickness of 12-25 μm; the interface modification layer is a nanoscale coupling agent coating with a thickness of 5-10 nm; the gradient aluminizing layer is an aluminum deposition layer with a gradient distribution of aluminum grain size with a thickness of 30-80 nm; the barrier reinforcement layer is an organic-inorganic composite coating with a thickness of 15-30 nm; the adhesive layer is a modified polyurethane adhesive layer with a thickness of 8-15 μm; and the heat-sealing layer is a high-temperature resistant PE film layer with a thickness of 40-100 μm.

[0008] The oxygen permeability of the composite membrane is ≤0.05cm. 3 / (m 2 •d•0.1MPa), water vapor transmission rate ≤0.1g / (m 2 •d) The aluminum layer adhesion is ≥1.8N / 15mm. After 72 hours of testing at 85℃ / 85%RH, there is no delamination or aluminum layer oxidation. After repeated bending 500 times, there is no aluminum layer cracking and the barrier performance decreases by no more than 10%. The heat resistance temperature can reach 120℃, which can meet the requirements of high-temperature cooking scenarios.

[0009] Preferably, the PET substrate layer is subjected to double-sided corona treatment, increasing the surface tension to 52-58 dynes / cm, and the surface roughness Ra ≤ 0.2μm. Furthermore, 0.3-0.8wt% of an antistatic agent and 0.5-1.2wt% of a heat-resistant modifier are added to the PET substrate layer. The antistatic agent is a quaternary ammonium salt antistatic agent, and the heat-resistant modifier is polyimide micropowder with a particle size of 50-100nm.

[0010] The PET substrate layer has an elongation at break of ≥80% and a tensile strength of ≥180MPa, effectively solving the technical problems of poor aluminum layer adhesion, insufficient heat resistance and easy deformation caused by insufficient surface tension of existing PET substrates, and easy generation of electrostatic adsorption of impurities affecting the quality of aluminum plating. At the same time, it improves the mechanical strength of the substrate and adapts to the tension requirements of subsequent aluminum plating and composite processes.

[0011] Preferably, the interface modification layer is composed of a silane coupling agent and a titanate coupling agent in a mass ratio of 3:1 to 5:1, wherein the silane coupling agent is γ-aminopropyltriethoxysilane and the titanate coupling agent is isopropyltristearate titanate.

[0012] The interface modification layer is uniformly coated on the surface of the PET substrate layer by roller coating and then dried at 100-120℃ for 3-5 minutes.

[0013] This interface modification layer can form a stable chemical bond between the PET substrate layer and the gradient aluminum plating layer, effectively alleviating the problem of interface stress concentration between the PET substrate and the aluminum layer, solving the defects of weak adhesion and easy delamination of the aluminum layer and the substrate in the prior art, while improving the deposition uniformity of the aluminum plating layer and reducing the generation of pinholes in the aluminum layer, laying the foundation for the subsequent preparation of the gradient aluminum plating layer.

[0014] Preferably, the gradient aluminum plating layer is prepared by a composite process of magnetron sputtering and vacuum evaporation. From the side near the interface modification layer to the side near the barrier reinforcement layer, the aluminum grain size gradually increases from 20-30nm to 50-60nm, and the relative density of the aluminum layer gradually increases from 0.92 to 0.98.

[0015] The gradient aluminum plating layer contains 0.5-1.0 wt% magnesium and 0.3-0.6 wt% zinc, with the magnesium and zinc elements uniformly dispersed in the intergranular spaces of the aluminum grains.

[0016] Compared to existing aluminum plating layers with a single thickness and single grain size, this gradient aluminum plating layer retains the flexibility of fine-grained aluminum layers, preventing cracking after repeated bending, while utilizing the high-density characteristics of coarse-grained aluminum layers to improve barrier performance. At the same time, the addition of magnesium and zinc elements further enhances the oxidation resistance and wear resistance of the aluminum layer, solving the problems of existing aluminum plating layers that are difficult to balance flexibility and barrier performance, are prone to oxidation, and have poor bending resistance. It also effectively reduces the number of pinholes in the aluminum layer, avoiding the problem of decreased barrier performance caused by the enlargement of pinholes.

[0017] Preferably, the barrier reinforcement layer is composed of polyvinylidene chloride (PVDC) and nano-silica in a mass ratio of 9:1-10:1, wherein the nano-silica has a particle size of 20-50 nm and has undergone surface modification treatment with a silane coupling agent; the barrier reinforcement layer is coated onto the surface of the gradient aluminum plating layer by vacuum spraying, and then cured at 110-130℃ for 5-8 minutes.

[0018] This barrier reinforcement layer can fill the tiny pinholes on the surface of the gradient aluminum-plated layer, forming a double barrier structure. This significantly improves the oxygen and water barrier properties of the composite film, solving the problem that the existing aluminum-plated composite film has weaker barrier properties than aluminum foil composite film and cannot meet the packaging requirements of products with long shelf life. At the same time, the addition of nano-silica can improve the wear resistance and high temperature resistance of the barrier reinforcement layer, avoiding the failure of barrier performance under high temperature environment.

[0019] Preferably, the adhesive layer is a modified waterborne polyurethane adhesive with a solid content of 35-45% and a viscosity of 1500-2500 mPa·s (25°C). The modified waterborne polyurethane adhesive contains 0.2-0.5 wt% of a crosslinking agent and 0.1-0.3 wt% of a defoamer. The crosslinking agent is an isocyanate crosslinking agent, and the defoamer is an organosilicon defoamer.

[0020] The adhesive layer is applied using a doctor blade coating method, with a coating amount of 8-12 g / m². 2 After coating, dry at 80-100℃ for 2-4 minutes;

[0021] This adhesive layer has good bonding strength and high temperature resistance, which can achieve a firm bond between the barrier reinforcement layer and the heat-sealing layer. It solves the problems of poor high temperature resistance, easy delamination during high-temperature cooking, and insufficient bonding strength of existing adhesives. At the same time, the water-based system is more environmentally friendly, meets the requirements of green production, and avoids the environmental pollution and safety hazards caused by solvent-based adhesives.

[0022] Preferably, the heat-sealing layer is composed of low-density PE and metallocene PE in a mass ratio of 7:3-8:2. The heat-sealing layer contains 0.3-0.6 wt% of an anti-blocking agent and 0.2-0.4 wt% of a heat-resistant stabilizer. The anti-blocking agent is silica micro powder, and the heat-resistant stabilizer is a hindered phenolic stabilizer.

[0023] The heat-sealing layer has a heat-sealing temperature of 120-140℃, a heat-sealing strength of ≥15N / 15mm, and an elongation at break of ≥150%. This heat-sealing layer has both good heat-sealing performance and high-temperature resistance, solving the defects of existing heat-sealing layers such as poor resistance to boiling, easy softening and deformation at high temperatures, and insufficient heat-sealing strength. At the same time, the addition of anti-blocking agent can prevent adhesion during the winding of the composite film, improve the processing convenience of the product, and meet the requirements of subsequent packaging and forming processes.

[0024] This invention also proposes a method for preparing a PET vacuum metallized composite film, comprising the following steps:

[0025] S1. Pretreatment of PET substrate: Select biaxially oriented PET film as substrate and perform double-sided corona treatment on it. Control the corona power to be 300-400W and the processing speed to be 20-30m / min, so that the surface tension of the substrate reaches 52-58 dynes / cm.

[0026] Subsequently, 0.3-0.8wt% antistatic agent and 0.5-1.2wt% heat-resistant modifier are added to the PET substrate in advance, and then dried at 80-100℃ for 10-15min to remove moisture and impurities from the substrate surface, thus obtaining the pretreated PET substrate layer.

[0027] S2. Preparation of the interface modification layer: Silane coupling agent and titanate coupling agent are compounded according to a preset ratio, diluted with deionized water to a mass concentration of 1-2%, stirred evenly, and then uniformly coated onto the surface of the pretreated PET substrate layer by roller coating, with a coating amount of 5-8 g / m². 2 It is then sent to a drying oven and dried at 100-120℃ for 3-5 minutes to form an interface modification layer;

[0028] S3. Gradient Aluminum Coating Layer Preparation: The PET substrate with the interface modification layer is fed into the vacuum aluminizing chamber. Initial evacuation is performed using a mechanical pump, followed by multi-stage vacuuming using a Roots pump and a diffusion pump to stabilize the vacuum level in the aluminizing chamber at ≤3×10⁻⁻⁻⁶. 3 Pa, substrate temperature in the aluminizing chamber ≤80℃; evaporation boat temperature 1350-1400℃;

[0029] A composite process of magnetron sputtering and vacuum evaporation is adopted. First, a fine-grained aluminum layer is deposited by magnetron sputtering, with the sputtering power controlled at 800-1000W and the sputtering time at 2-3min. Then, a coarse-grained aluminum layer is deposited by vacuum evaporation, with the aluminum wire feed speed controlled at 0.4-1.0m / min, the evaporation boat temperature at 1350-1400℃, and the deposition time at 3-5min. Magnesium and zinc elements are added simultaneously during the deposition process to form a gradient aluminum plating layer.

[0030] After aluminum plating is completed, nitrogen is introduced into the aluminum plating chamber in stages. The first time, nitrogen is introduced to a pressure of 800-1200 Pa and maintained for 8-12 hours. The nitrogen is then introduced again to a pressure of 1300-1500 Pa and maintained for at least 12 hours to improve the stability of the aluminum layer.

[0031] S4. Preparation of barrier reinforcement layer: Polyvinylidene chloride and surface-modified nano-silica are mixed in a preset ratio, and an organic solvent is added and stirred evenly to form a coating liquid.

[0032] The coating liquid is uniformly applied to the surface of the gradient aluminum plating layer by vacuum spraying, with a coating amount of 10-15 g / m². 2 It is then placed in a curing oven and cured at 110-130℃ for 5-8 minutes to form a barrier reinforcement layer;

[0033] S5. Adhesive layer and heat-sealing layer composite: Add the modified waterborne polyurethane adhesive to the crosslinking agent and defoamer, stir evenly, and then apply it to the surface of the barrier reinforcement layer by scraper coating. The coating amount is 8-12 g / m². 2 After drying at 80-100℃ for 2-4 minutes, an adhesive layer is formed; then the heat-sealing layer and the adhesive layer are aligned and fed into a laminating machine, with the laminating temperature controlled at 100-120℃, the laminating pressure at 0.3-0.5MPa, and the laminating speed at 15-25m / min, to achieve a firm lamination between the heat-sealing layer and the adhesive layer.

[0034] S6. Post-processing: The laminated film is fed into a cooling roller for cooling, with the roller temperature controlled at 0-5℃. After cooling, the total film thickness is monitored using an online thickness measurement system to ensure it is 100-200μm. Subsequently, the film is slit and wound up using a dual-station winding system, with the winding tension controlled at 0.8-1.5N / m. 2As the roll diameter increases, the pressure of the pressure roller decreases linearly, ensuring that the end face flatness error is ≤0.3mm, thus obtaining a PET vacuum metallized composite film.

[0035] Preferably, in step S3, a dynamic tension control system is used during the magnetron sputtering process. The tension is automatically adjusted by a PLC controller to control the substrate tension fluctuation within ±0.1 N / m. 2 Within ±5%; During the vacuum evaporation process, a laser displacement sensor is used to monitor the aluminum layer thickness in real time, and the evaporation current and aluminum feeding speed are automatically adjusted to keep the aluminum layer thickness fluctuation range within ±5%.

[0036] In step S5, after lamination is completed, an online testing system is used to test the adhesion, barrier properties and heat-sealing strength of the composite film. Unqualified products are reworked.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] This invention designs a multi-layer composite structure consisting of a PET substrate layer, an interface modification layer, a gradient aluminized layer, a barrier reinforcement layer, an adhesive layer, and a heat-sealing layer. The synergistic effect of each layer significantly improves the overall performance of the composite film.

[0039] Among them, the interface modification layer adopts a compound system of silane coupling agent and titanate coupling agent, which solves the problems of poor interface modification effect and weak adhesion between aluminum layer and substrate of existing single coupling agent, forms a stable chemical bond, and reduces aluminum layer peeling.

[0040] The gradient aluminum coating uses a composite process of magnetron sputtering and vacuum evaporation to achieve a gradient distribution of aluminum grain size, which takes into account both the flexibility of fine grains and the barrier properties of coarse grains. The addition of magnesium and zinc elements further enhances the oxidation resistance and wear resistance of the aluminum layer, solving the pain points of existing aluminum coatings that are prone to cracking, oxidation, and insufficient barrier properties.

[0041] The barrier reinforcement layer adopts a composite system of PVDC and surface-modified nano-silica, which can fill the tiny pinholes on the surface of the aluminum-plated layer to form a double barrier structure, significantly improving oxygen and water barrier performance. This solves the defects of existing aluminum-plated composite films, which have weaker barrier performance than aluminum foil composite films and cannot meet the packaging requirements of long-shelf-life products.

[0042] The adhesive layer uses a modified water-based polyurethane adhesive, which has both good bonding strength and high temperature resistance, preventing delamination during high-temperature cooking, and is environmentally friendly and pollution-free.

[0043] The heat-sealing layer uses a composite system of LDPE and mPE, with added anti-blocking agents and heat-resistant stabilizers to improve its resistance to boiling and heat-sealing performance, making it suitable for packaging molding processes.

[0044] This invention uses dynamic tension control and laser thickness monitoring to solve problems such as poor uniformity of aluminum layer thickness, cracking of aluminum layer caused by tension imbalance, and weak composite bonding in existing preparation processes, thereby improving the product qualification rate; optimizing process steps, shortening production cycle, reducing production costs, and the entire process is environmentally friendly and pollution-free, meeting the needs of large-scale industrial production.

[0045] The PET vacuum metallized composite film prepared by this invention has low oxygen permeability and water vapor permeability, strong aluminum layer adhesion, and excellent resistance to boiling, bending, and high temperature. It can be widely used in the packaging of high-temperature cooked food, pharmaceuticals, precision electronic components, and other products, and has broad market application prospects. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the layered structure of the PET vacuum metallized composite film of the present invention.

[0047] In the diagram: 1 PET substrate layer, 2 interface modification layer, 3 gradient aluminized layer, 4 barrier reinforcement layer, 5 adhesive layer, 6 heat seal layer. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0049] Example 1

[0050] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer 1, an interface modification layer 2, a gradient metallized layer 3, a barrier reinforcement layer 4, an adhesive layer 5, and a heat-sealing layer 6. The parameters of each layer are as follows:

[0051] PET substrate layer 1: Biaxially oriented PET film, 12 μm thick, double-sided corona treatment, surface tension 52 dynes / cm, surface roughness Ra=0.18 μm, with 0.3 wt% quaternary ammonium salt antistatic agent and 0.5 wt% polyimide micro powder, particle size 50 nm, elongation at break 80%, tensile strength 180 MPa.

[0052] Interface modification layer 2: γ-aminopropyltriethoxysilane and isopropyltristearate titanate are compounded at a mass ratio of 3:1, with a thickness of 5 nm, coated by roller coating, dried at 100℃ for 3 min, and a coating amount of 5 g / m. 2 The coupling agent solution has a mass concentration of 1%.

[0053] Gradient aluminum layer 3: 30nm thick, prepared using a composite process of magnetron sputtering and vacuum evaporation, with aluminum grain size gradually increasing from 20nm to 50nm, and aluminum layer density increasing from 2.6g / cm³. 3The gradient was increased to 2.7 g / cm³. 3 Add 0.5wt% magnesium and 0.3wt% zinc;

[0054] Vacuum degree of aluminizing chamber: 3×10⁻ 3 Pa, temperature 1250℃, magnetron sputtering power 800W, time 2min, vacuum evaporation aluminum wire feeding speed 0.4m / min, evaporation boat temperature 1350℃, deposition time 3min; after aluminum plating, nitrogen was charged in stages, first charged to 800Pa and maintained for 8h, then charged to 1300Pa and maintained for 12h.

[0055] Barrier reinforcement layer 4: PVDC and surface-modified nano-silica with a particle size of 20nm are composited at a mass ratio of 9:1, with a thickness of 15nm. Vacuum spraying is used for coating, followed by curing at 110℃ for 5 minutes. The coating amount is 10g / m². 2 ;

[0056] Adhesive layer 5: Modified waterborne polyurethane adhesive, solid content 35%, viscosity 1500 mPa·s at 25℃, with 0.2 wt% isocyanate crosslinking agent and 0.1 wt% silicone defoamer added, applied by doctor blade, coating amount 8 g / m². 2 Dry at 80℃ for 2 minutes;

[0057] Heat-sealing layer 6: LDPE and mPE are compounded in a mass ratio of 7:3, with a thickness of 40μm. 0.3wt% silica micro powder anti-blocking agent and 0.2wt% hindered phenolic heat-resistant stabilizer are added. The heat-sealing temperature is 120℃, the heat-sealing strength is 15N / 15mm, and the elongation at break is 150%. The total thickness of the composite film is 100μm.

[0058] The above-mentioned composite film is prepared as follows: according to the above parameters, the following steps are performed in sequence: PET substrate pretreatment, interface modification layer 2 preparation, gradient aluminum plating layer 3 preparation, barrier reinforcement layer 4 preparation, bonding layer 5 and heat sealing layer 6 lamination, and post-treatment; wherein, the substrate pretreatment corona power is 300W, the processing speed is 20m / min, the drying temperature is 80℃, and the time is 10min.

[0059] Magnetron sputtering employs dynamic tension control, with tension fluctuations of ±0.1 N / m. 2 within;

[0060] Vacuum evaporation uses laser thickness monitoring, with thickness fluctuations within ±5%.

[0061] The combined temperature is 100℃, the pressure is 0.3MPa, and the speed is 15m / min.

[0062] Cooling roller temperature 0℃, winding tension 0.8N / m 2 The end face flatness error is ≤0.3mm.

[0063] Example 2

[0064] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer 1, an interface modification layer 2, a gradient metallized layer 3, a barrier reinforcement layer 4, an adhesive layer 5, and a heat-sealing layer 6. The parameters of each layer are as follows:

[0065] PET substrate layer 1: Biaxially oriented PET film, 18 μm thick, double-sided corona treatment, surface tension 55 dynes / cm, surface roughness Ra=0.15 μm, with 0.5 wt% quaternary ammonium salt antistatic agent and 0.8 wt% polyimide micro powder, particle size 70 nm, elongation at break 85%, tensile strength 190 MPa.

[0066] Interface modification layer 2: γ-aminopropyltriethoxysilane and isopropyltristearate titanate were compounded at a mass ratio of 4:1, with a thickness of 7 nm, coated by roller coating, dried at 110 °C for 4 min, and a coating amount of 6 g / m. 2 The coupling agent solution has a mass concentration of 1.5%.

[0067] Gradient aluminum layer 3: 50nm thick, prepared using a composite process of magnetron sputtering and vacuum evaporation, with aluminum grain size gradually increasing from 25nm to 55nm, and aluminum layer density increasing from 2.6g / cm³. 3 The gradient was increased to 2.7 g / cm³. 3 Add 0.7wt% magnesium and 0.4wt% zinc;

[0068] Vacuum degree of aluminizing chamber: 2×10⁻ 3 Pa, temperature 1300℃, magnetron sputtering power 900W, time 2.5min, vacuum evaporation aluminum wire feeding speed 0.7m / min, evaporation boat temperature 1375℃, deposition time 4min; after aluminum plating, nitrogen was charged in stages, first charged to 1000Pa and maintained for 10h, then charged to 1400Pa and maintained for 14h.

[0069] Barrier reinforcement layer 4: PVDC and surface-modified nano-silica with a particle size of 35nm are composited at a mass ratio of 9.5:1, with a thickness of 22nm. Vacuum spraying is used for coating, followed by curing at 120℃ for 6.5min. The coating amount is 12g / m². 2 ;

[0070] Adhesive layer 5: Modified waterborne polyurethane adhesive, solid content 40%, viscosity 2000 mPa·s at 25℃, with the addition of 0.3 wt% isocyanate crosslinking agent and 0.2 wt% silicone defoamer, applied by doctor blade, coating amount 10 g / m². 2 Dry at 90℃ for 3 minutes;

[0071] Heat-sealing layer 6: LDPE and mPE are composited at a mass ratio of 7.5:2.5, with a thickness of 70μm. 0.4wt% silica micro powder anti-blocking agent and 0.3wt% hindered phenolic heat-resistant stabilizer are added. The heat-sealing temperature is 130℃, the heat-sealing strength is 18N / 15mm, and the elongation at break is 160%. The total thickness of the composite film is 150μm.

[0072] The above-mentioned composite film is prepared by performing the following steps in sequence according to the above parameters: PET substrate pretreatment, interface modification layer 2 preparation, gradient aluminum plating layer 3 preparation, barrier reinforcement layer 4 preparation, bonding layer 5 and heat sealing layer 6 composite, and post-treatment.

[0073] Among them, the substrate pretreatment corona power is 350W, the processing speed is 25m / min, the drying temperature is 90℃, and the time is 12min;

[0074] Magnetron sputtering employs dynamic tension control, with tension fluctuations of ±0.1 N / m. 2 within;

[0075] Vacuum evaporation uses laser thickness monitoring, with thickness fluctuations within ±5%.

[0076] The combined temperature is 110℃, the pressure is 0.4MPa, and the speed is 20m / min.

[0077] Cooling roller temperature 3℃, winding tension 1.2N / m 2 The end face flatness error is ≤0.3mm.

[0078] Example 3

[0079] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer 1, an interface modification layer 2, a gradient metallized layer 3, a barrier reinforcement layer 4, an adhesive layer 5, and a heat-sealing layer 6. The parameters of each layer are as follows:

[0080] PET substrate layer 1: Biaxially oriented PET film, 20 μm thick, double-sided corona treatment, surface tension 56 dynes / cm, surface roughness Ra=0.12 μm, with 0.6 wt% quaternary ammonium salt antistatic agent and 1.0 wt% polyimide micro powder with a particle size of 80 nm, elongation at break 90%, tensile strength 200 MPa;

[0081] Interface modification layer 2: γ-aminopropyltriethoxysilane and isopropyltristearate titanate were compounded at a mass ratio of 4.5:1, with a thickness of 8 nm, coated by roller coating, and dried at 115℃ for 4 min, with a coating amount of 7 g / m. 2 The coupling agent solution concentration was 1.8%;

[0082] Gradient aluminum layer 3: 60nm thick, prepared using a composite process of magnetron sputtering and vacuum evaporation, with aluminum grain size gradually increasing from 28nm to 58nm, and aluminum layer density increasing from 2.6g / cm³. 3 The gradient was increased to 2.7 g / cm³. 3 Add 0.8 wt% magnesium and 0.5 wt% zinc;

[0083] Vacuum degree of aluminizing chamber: 1×10⁻ 3 Pa, temperature 1300℃, magnetron sputtering power 950W, time 2.8min, vacuum evaporation aluminum wire feed speed 0.8m / min, evaporation boat temperature 1380℃, deposition time 4.5min; after aluminum plating, nitrogen was charged in stages, first charged to 1100Pa and maintained for 11h, then charged to 1450Pa and maintained for 15h.

[0084] Barrier reinforcement layer 4: PVDC and surface-modified nano-silica, 40nm particle size, composited at a mass ratio of 9.8:1, 25nm thick, vacuum sprayed, cured at 125℃ for 7min, coating amount 13g / m². 2 ;

[0085] Adhesive layer 5: Modified waterborne polyurethane adhesive, solid content 42%, viscosity 2200 mPa·s at 25℃, with the addition of 0.4 wt% isocyanate crosslinking agent and 0.25 wt% silicone defoamer, applied by doctor blade, coating amount 11 g / m². 2 Dry at 95℃ for 3.5 minutes;

[0086] Heat-sealing layer 6: LDPE and mPE are composited at a mass ratio of 7.8:2.2, with a thickness of 80μm. 0.5wt% silica micro powder anti-blocking agent and 0.35wt% hindered phenolic heat-resistant stabilizer are added. The heat-sealing temperature is 135℃, the heat-sealing strength is 20N / 15mm, and the elongation at break is 170%. The total thickness of the composite film is 180μm.

[0087] The above-mentioned composite film is prepared by performing the following steps in sequence according to the above parameters: PET substrate pretreatment, interface modification layer 2 preparation, gradient aluminum plating layer 3 preparation, barrier reinforcement layer 4 preparation, bonding layer 5 and heat sealing layer 6 composite, and post-treatment.

[0088] Among them, the substrate pretreatment corona power is 380W, the processing speed is 28m / min, the drying temperature is 95℃, and the time is 13min;

[0089] Magnetron sputtering employs dynamic tension control, with tension fluctuations of ±0.1 N / m. 2 within;

[0090] Vacuum evaporation uses laser thickness monitoring, with thickness fluctuations within ±5%.

[0091] The combined temperature was 115℃, the pressure was 0.45MPa, and the speed was 23m / min.

[0092] Cooling roller temperature 4℃, winding tension 1.3N / m 2 The flatness error of the end face is ≤0.3mm;

[0093] After lamination, an online testing system is used for inspection, and unqualified products are reworked.

[0094] Example 4

[0095] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer 1, an interface modification layer 2, a gradient metallized layer 3, a barrier reinforcement layer 4, an adhesive layer 5, and a heat-sealing layer 6. The parameters of each layer are as follows:

[0096] PET substrate layer 1: Biaxially oriented PET film, 22 μm thick, double-sided corona treatment, surface tension 57 dynes / cm, surface roughness Ra=0.10 μm, with 0.7 wt% quaternary ammonium salt antistatic agent and 1.1 wt% polyimide micro powder, particle size 90 nm, elongation at break 95%, tensile strength 210 MPa.

[0097] Interface modification layer 2: γ-aminopropyltriethoxysilane and isopropyltristearate titanate were compounded at a mass ratio of 4.8:1, with a thickness of 9 nm, coated by roller coating, and dried at 118℃ for 4.5 min, with a coating amount of 7.5 g / m. 2 The coupling agent solution concentration was 1.9%;

[0098] Gradient aluminum layer 3: 70nm thick, prepared using a composite process of magnetron sputtering and vacuum evaporation, with aluminum grain size gradually increasing from 29nm to 59nm, and aluminum layer density increasing from 2.6g / cm³. 3 The gradient was increased to 2.7 g / cm³. 3 Add 0.9 wt% magnesium and 0.55 wt% zinc;

[0099] Vacuum degree of aluminizing chamber: 1×10⁻ 3 Pa, temperature 1320℃, magnetron sputtering power 980W, time 2.9min, vacuum evaporation aluminum wire feed speed 0.9m / min, evaporation boat temperature 1390℃, deposition time 4.8min;

[0100] After aluminum plating, nitrogen was charged in stages. The first nitrogen charge was 1150 Pa and maintained for 11.5 h, and the second nitrogen charge was 1480 Pa and maintained for 15.5 h.

[0101] Barrier reinforcement layer 4: PVDC and surface-modified nano-silica with a particle size of 45nm are composited at a mass ratio of 9.9:1, with a thickness of 28nm. Vacuum spraying is used for coating, followed by curing at 128℃ for 7.5min. The coating amount is 14g / m².2 ;

[0102] Adhesive layer 5: Modified waterborne polyurethane adhesive, solid content 44%, viscosity 2400 mPa·s at 25℃, with the addition of 0.45 wt% isocyanate crosslinking agent and 0.28 wt% silicone defoamer, applied by doctor blade, coating amount 11.5 g / m². 2 Dry at 98℃ for 3.8 min;

[0103] Heat-sealing layer 6: LDPE and mPE are composited at a mass ratio of 7.9:2.1, with a thickness of 90μm. 0.55wt% silica micro powder anti-blocking agent and 0.38wt% hindered phenolic heat-resistant stabilizer are added. The heat-sealing temperature is 138℃, the heat-sealing strength is 21N / 15mm, and the elongation at break is 175%. The total thickness of the composite film is 190μm.

[0104] The above-mentioned composite film is prepared by performing the following steps in sequence according to the above parameters: PET substrate pretreatment, interface modification layer 2 preparation, gradient aluminum plating layer 3 preparation, barrier reinforcement layer 4 preparation, bonding layer 5 and heat sealing layer 6 composite, and post-treatment.

[0105] Among them, the substrate pretreatment corona power is 390W, the processing speed is 29m / min, the drying temperature is 98℃, and the time is 14min;

[0106] Magnetron sputtering employs dynamic tension control, with tension fluctuations of ±0.1 N / m. 2 Within ±5%; vacuum evaporation uses laser thickness monitoring, and the thickness fluctuation is within ±5%.

[0107] The combined temperature was 118℃, the pressure was 0.48MPa, and the speed was 24m / min.

[0108] Cooling roller temperature 4.5℃, winding tension 1.4N / m 2 The flatness error of the end face is ≤0.3mm; after lamination, an online inspection system is used for inspection, and unqualified products are reworked.

[0109] Example 5

[0110] A PET vacuum metallized composite film comprises, from the outside to the inside, a PET substrate layer 1, an interface modification layer 2, a gradient metallized layer 3, a barrier reinforcement layer 4, an adhesive layer 5, and a heat-sealing layer 6. The parameters of each layer are as follows:

[0111] PET substrate layer 1: Biaxially oriented PET film, 25 μm thick, double-sided corona treatment, surface tension 58 dynes / cm, surface roughness Ra=0.08 μm, with 0.8 wt% quaternary ammonium salt antistatic agent and 1.2 wt% polyimide micro powder with a particle size of 100 nm, elongation at break 100%, tensile strength 220 MPa;

[0112] Interface modification layer 2: γ-aminopropyltriethoxysilane and isopropyltristearate titanate are compounded at a mass ratio of 5:1, with a thickness of 10 nm, coated by roller coating, dried at 120 °C for 5 min, and the coating amount is 8 g / m². 2 The coupling agent solution has a mass concentration of 2%.

[0113] Gradient aluminum layer 3: 80nm thick, prepared using a composite process of magnetron sputtering and vacuum evaporation, with aluminum grain size gradually increasing from 30nm to 60nm, and aluminum layer density increasing from 2.6g / cm³. 3 The gradient was increased to 2.7 g / cm³. 3 1.0 wt% magnesium and 0.6 wt% zinc were added; the vacuum degree of the aluminizing chamber was 1×10⁻ 3 Pa, temperature 1350℃, magnetron sputtering power 1000W, time 3min, vacuum evaporation aluminum wire feeding speed 1.0m / min, evaporation boat temperature 1400℃, deposition time 5min; after aluminum plating, nitrogen was charged in stages, first charged to 1200Pa and maintained for 12h, then charged to 1500Pa and maintained for 16h.

[0114] Barrier reinforcement layer 4: PVDC and surface-modified nano-silica with a particle size of 50nm are composited at a mass ratio of 10:1, with a thickness of 30nm. Vacuum spraying is used for coating, followed by curing at 130℃ for 8 minutes. The coating amount is 15g / m². 2 ;

[0115] Adhesive layer 5: Modified waterborne polyurethane adhesive, solid content 45%, viscosity 2500 mPa·s at 25℃, with the addition of 0.5 wt% isocyanate crosslinking agent and 0.3 wt% silicone defoamer, applied by doctor blade, coating amount 12 g / m². 2 Dry at 100℃ for 4 minutes;

[0116] Heat-sealing layer 6: LDPE and mPE are compounded at a mass ratio of 8:2, with a thickness of 100μm. 0.6wt% silica micro powder anti-blocking agent and 0.4wt% hindered phenolic heat-resistant stabilizer are added. The heat-sealing temperature is 140℃, the heat-sealing strength is 22N / 15mm, and the elongation at break is 180%. The total thickness of the composite film is 200μm.

[0117] The above-mentioned composite film is prepared by performing the following steps in sequence according to the above parameters: PET substrate pretreatment, interface modification layer 2 preparation, gradient aluminum plating layer 3 preparation, barrier reinforcement layer 4 preparation, bonding layer 5 and heat sealing layer 6 composite, and post-treatment.

[0118] The substrate pretreatment corona power was 400W, the processing speed was 30m / min, the drying temperature was 100℃, and the time was 15min.

[0119] Magnetron sputtering employs dynamic tension control, with tension fluctuations of ±0.1 N / m.2 Within ±5%; vacuum evaporation uses laser thickness monitoring, and the thickness fluctuation is within ±5%.

[0120] The combined temperature is 120℃, the pressure is 0.5MPa, and the speed is 25m / min.

[0121] Cooling roller temperature 5℃, winding tension 1.5N / m 2 The flatness error of the end face is ≤0.3mm; after lamination, an online inspection system is used for inspection, and unqualified products are reworked.

[0122] To verify the performance of each embodiment of the present invention, the PET vacuum metallized composite film prepared in the above 5 embodiments was subjected to performance tests. The test items included: oxygen permeability, water vapor permeability, aluminum layer adhesion, damp heat resistance, bending resistance, heat resistance temperature, heat sealing strength, and product qualification rate. The test methods were all carried out in accordance with relevant national standards. The specific experimental data are shown in the table below.

[0123]

[0124] The above experimental data show that:

[0125] The oxygen and water vapor transmission rates of Examples 1-5 all meet industry standard requirements, with the oxygen transmission rate of Example 3 being 0.035 cm⁻¹. 3 / (m 2 ·d·0.1MPa) and water vapor transmission rate 0.070g / (m 2 •d) The lowest value is significantly better than other embodiments, indicating that the gradient aluminum plating layer 3 and the barrier reinforcement layer 4 in Embodiment 3 have the best synergistic effect, which can effectively fill the pinholes in the aluminum layer, form a highly efficient double barrier structure, and improve the barrier performance.

[0126] The aluminum layer adhesion of Examples 1-5 all met industry standards. The aluminum layer adhesion of Example 3 was 2.8 N / 15 mm, which was much higher than that of other examples. This is because the interface modification layer 2 of Example 3 adopted the optimal ratio of coupling agent compound system and the process parameters were precisely controlled, which formed a more stable chemical bond between the PET substrate and the gradient aluminum plating layer 3, effectively improving the interface bonding force and preventing the aluminum layer from falling off.

[0127] In Example 1, there was slight oxidation of the aluminum layer. In Examples 2-5, there was no delamination, no obvious oxidation, or no oxidation. In Example 3, the aluminum layer showed no oxidation. This indicates that the ratio of magnesium and zinc in the gradient aluminum plating layer 3 of Example 3 was optimal, and the staged nitrogen purging process after aluminum plating was more reasonable, which effectively improved the oxidation resistance and stability of the aluminum layer.

[0128] Examples 1-5 showed no aluminum layer cracking, and the barrier performance degradation did not exceed 10%. Among them, the barrier performance degradation of Example 3 was only 3%, which was significantly lower than that of the other examples. This indicates that the gradient aluminum layer 3 in Example 3 has the optimal grain size gradient distribution design, which takes into account the flexibility of fine grains and the barrier performance of coarse grains, effectively reduces stress concentration during bending, and avoids a significant degradation of barrier performance.

[0129] The heat resistance temperature of Example 1 was 115℃, which did not meet the industry standard requirements. Examples 2-5 all met the standard. Among them, the heat resistance temperature of Example 3 reached 125℃, which was higher than the other examples. This indicates that the addition ratio of heat-resistant modifier in PET substrate layer 1, the formulation and process parameters of adhesive layer 5 and heat-sealing layer 6 in Example 3 were optimal, which synergistically improved the high temperature resistance of the composite film and made it more suitable for high-temperature cooking scenarios.

[0130] The heat seal strength of Examples 1-5 all meet industry standards. The heat seal strength of Examples 4 and 5 is slightly higher than that of Example 3, but the difference is small. However, Example 3 has better overall performance, and its heat seal strength fully meets the requirements for packaging.

[0131] The product qualification rate of Example 3 reached 99%, which is much higher than that of other examples. The preparation process parameters of Example 3 were controlled most precisely. Dynamic tension control, laser thickness monitoring, and online detection were adopted to effectively reduce problems such as uneven aluminum layer thickness, tension imbalance, and weak composite, thereby improving product consistency and qualification rate.

[0132] In summary, the PET vacuum metallized composite film of Example 3 outperforms other examples in key indicators such as barrier performance, aluminum layer adhesion, damp heat resistance, bending resistance, heat resistance temperature, and product qualification rate, and has the best overall performance.

[0133] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A PET vacuum metallized composite film, comprising, from the outside to the inside, a PET substrate layer (1), an interface modification layer (2), a gradient metallized layer (3), a barrier reinforcement layer (4), an adhesive layer (5), and a heat-sealing layer (6). The PET substrate layer (1) is a biaxially oriented PET film with a thickness of 12-25 μm. The interface modification layer (2) is a nano-coupling agent coating with a thickness of 5-10 nm. The gradient aluminized layer (3) is an aluminum deposition layer with a gradient distribution of aluminum grain size and a thickness of 30-80 nm. The barrier reinforcement layer (4) is an organic-inorganic composite coating with a thickness of 15-30 nm. The adhesive layer (5) is a modified polyurethane adhesive layer with a thickness of 8-15 μm. The heat-sealing layer (6) is a high-temperature resistant PE film layer with a thickness of 40-100 μm.

2. The PET vacuum metallized composite film according to claim 1, characterized in that, The PET substrate layer (1) is subjected to double-sided corona treatment, which increases the surface tension to 52-58 dynes / cm and the surface roughness Ra≤0.2μm. In addition, 0.3-0.8wt% of antistatic agent and 0.5-1.2wt% of heat-resistant modifier are added to the PET substrate layer (1). The antistatic agent is a quaternary ammonium salt antistatic agent and the heat-resistant modifier is polyimide micro powder with a particle size of 50-100nm.

3. The PET vacuum metallized composite film according to claim 2, characterized in that, The interface modification layer (2) is composed of a silane coupling agent and a titanate coupling agent in a mass ratio of 3:1-5:

1. The silane coupling agent is γ-aminopropyltriethoxysilane, and the titanate coupling agent is isopropyltristearate titanate. The interface modification layer (2) is uniformly coated on the surface of the PET substrate layer (1) by roller coating and then dried at 100-120℃ for 3-5 minutes.

4. The PET vacuum metallized composite film according to claim 1, characterized in that, The gradient aluminum plating layer (3) is prepared by a composite process of magnetron sputtering and vacuum evaporation. From the side near the interface modification layer (2) to the side near the barrier reinforcement layer (4), the aluminum grain size increases from 20-30nm to 50-60nm, and the relative density of the aluminum layer increases from 0.92 to 0.

98. The gradient aluminum plating layer (3) contains 0.5-1.0 wt% magnesium and 0.3-0.6 wt% zinc, with the magnesium and zinc elements uniformly dispersed in the gaps between aluminum grains.

5. The PET vacuum metallized composite film according to claim 1, characterized in that, The barrier reinforcement layer (4) is composed of polyvinylidene chloride and nano-silica in a mass ratio of 9:1-10:

1. The nano-silica has a particle size of 20-50nm and is surface modified by silane coupling agent. The barrier reinforcement layer (4) is coated onto the surface of the gradient aluminum plating layer (3) by vacuum spraying. After coating, it is cured at 110-130℃ for 5-8 minutes.

6. The PET vacuum metallized composite film according to claim 1, characterized in that, The adhesive layer (5) is a modified waterborne polyurethane adhesive with a solid content of 35-45% and a viscosity of 1500-2500 mPa·s. The modified waterborne polyurethane adhesive contains 0.2-0.5 wt% of a crosslinking agent and 0.1-0.3 wt% of a defoamer. The crosslinking agent is an isocyanate crosslinking agent, and the defoamer is an organosilicon defoamer. The adhesive layer (5) is coated by means of a doctor blade, with a coating amount of 8-12 g / m 2 and is dried at 80-100°C for 2-4 minutes after coating.

7. The PET vacuum metallized composite film according to claim 1, characterized in that, The heat-sealing layer (6) is composed of low-density PE and metallocene PE in a mass ratio of 7:3-8:

2. The heat-sealing layer (6) contains 0.3-0.6 wt% anti-blocking agent and 0.2-0.4 wt% heat-resistant stabilizer. The anti-blocking agent is silica micro powder and the heat-resistant stabilizer is hindered phenolic stabilizer. The heat sealing temperature of the heat sealing layer (6) is 120-140℃, the heat sealing strength is ≥15N / 15mm, and the elongation at break is ≥150%.

8. A method for preparing a PET vacuum metallized composite film, used to prepare the PET vacuum metallized composite film according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Pretreatment of PET substrate: Select biaxially oriented PET film as substrate and perform double-sided corona treatment on it. Control the corona power to be 300-400W and the processing speed to be 20-30m / min, so that the surface tension of the substrate reaches 52-58 dynes / cm. Subsequently, 0.3-0.8wt% antistatic agent and 0.5-1.2wt% heat-resistant modifier were added to the PET substrate in advance, and dried at 80-100℃ for 10-15min to remove moisture and impurities from the surface of the substrate, thus obtaining the pretreated PET substrate layer (1). S2, interface modification layer (2) preparation: the silane coupling agent and titanate coupling agent are compounded according to a preset ratio, deionized water is added for dilution to a mass concentration of 1-2%, and after uniform stirring, the surface of the pretreated PET substrate layer (1) is uniformly coated by roll coating, the coating amount is 5-8 g / m 2 , and then sent to a drying oven, dried at 100-120 DEG C for 3-5 min, forming an interface modification layer (2); S3, Gradient aluminum plating layer (3) preparation: the PET substrate with interface modification layer (2) is sent into the vacuum aluminum plating chamber, first, initial pumping is carried out by using a mechanical pump, then, multi-stage vacuum pumping is carried out by using a Roots pump and a diffusion pump, so that the vacuum degree in the aluminum plating chamber is stabilized at ≤3×10⁻ 3 Pa, the substrate temperature in the aluminum plating chamber is ≤80℃, the evaporation boat temperature is 1350-1400℃; A composite process of magnetron sputtering and vacuum evaporation was adopted. First, a fine-grained aluminum layer was deposited by magnetron sputtering with a sputtering power of 800-1000W and a sputtering time of 2-3min. Then, a coarse-grained aluminum layer was deposited by vacuum evaporation with an aluminum wire feeding speed of 0.4-1.0m / min, an evaporation boat temperature of 1350-1400℃, and a deposition time of 3-5min. Magnesium and zinc elements were added simultaneously during the deposition process to form a gradient aluminum layer (3). After aluminum plating is completed, nitrogen is introduced into the aluminum plating chamber in stages. The first time, nitrogen is introduced to a pressure of 800-1200 Pa and maintained for 8-12 hours. The nitrogen is then introduced again to a pressure of 1300-1500 Pa and maintained for at least 12 hours to improve the stability of the aluminum layer. S4, Barrier Reinforcement Layer (4) Preparation: Polyvinylidene chloride and surface-modified nano-silica are mixed in a preset ratio, and an organic solvent is added and stirred evenly to form a coating liquid; The coating liquid was uniformly applied to the surface of the gradient aluminum layer (3) by vacuum spraying, with a coating amount of 10-15 g / m. 2 Then it is sent into a curing oven and cured at 110-130℃ for 5-8 minutes to form a barrier reinforcement layer (4). S5. Composite of adhesive layer (5) and heat-sealing layer (6): Modified waterborne polyurethane adhesive is added to crosslinking agent and defoamer, stirred evenly, and then coated onto the surface of barrier reinforcement layer (4) by scraper coating method, with a coating amount of 8-12 g / m 2 After drying at 80-100℃ for 2-4 minutes, an adhesive layer (5) is formed; then the heat-sealing layer (6) is aligned with the adhesive layer (5) and sent into the laminating machine. The laminating temperature is controlled at 100-120℃, the laminating pressure is 0.3-0.5MPa, and the laminating speed is 15-25m / min, so as to achieve a firm lamination between the heat-sealing layer (6) and the adhesive layer (5). S6. Post-processing: The laminated film is fed into a cooling roller for cooling, with the roller temperature controlled at 0-5℃. After cooling, the total film thickness is monitored using an online thickness measurement system to ensure it is 100-200μm. Subsequently, the film is slit and wound up using a dual-station winding system, with the winding tension controlled at 0.8-1.5N / m. 2 As the roll diameter increases, the pressure of the pressure roller decreases linearly, ensuring that the end face flatness error is ≤0.3mm, thus obtaining a PET vacuum metallized composite film.

9. The method for preparing a PET vacuum metallized composite film according to claim 8, characterized in that, In step S3, a dynamic tension control system is used during magnetron sputtering. The tension is automatically adjusted by a PLC controller to control the substrate tension fluctuation within ±0.1 N / m. 2 within; During the vacuum evaporation process, a laser displacement sensor is used to monitor the aluminum layer thickness in real time and automatically adjust the evaporation current and aluminum feeding speed to keep the aluminum layer thickness fluctuation range within ±5%. In step S5, after the composite is completed, an online testing system is used to test the adhesion, barrier properties and heat-sealing strength of the composite film. Unqualified products are reworked.

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