Modified BOPET (Biaxially Oriented Polyethylene Terephthalate) transparent high-barrier-property composite film and preparation method thereof

Abstract

The invention relates to the technical field of composite films, and discloses a modified BOPET transparent high-barrier-property composite film and a preparation method thereof.The modified BOPET transparent high-barrier-property composite film comprises a BOPET base layer, modified barrier layers arranged on the two sides of the BOPET base layer and protective layers arranged on the outer sides of the modified barrier layers.The modified barrier layers are arranged on the two sides of the BOPET base layer, so that the barrier property of the film is improved, and the barrier property of the film is improved; according to the present invention, the antibacterial property and the ultraviolet ray barrier property of the film are enhanced by adding the nano-silica and the nano-silver, the barrier property and the chemical corrosion resistance of the film are further improved by using the polyvinylidene chloride coating as the protection layer, and the preparation method is simple, easy to operate and suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of composite films, and in particular to a modified BOPET transparent high-barrier composite film and a preparation method thereof. Background Art

[0002] With the continuous advancement and innovation of science and technology, the requirements of various industries for packaging materials are gradually increasing. Especially in key areas such as food, medicine, and electronics, the performance requirements for packaging films are even more stringent; these areas require the use of packaging films with high barrier properties to ensure that products are protected from the invasion and influence of oxygen, water vapor, ultraviolet rays, and other harmful substances during storage and transportation; in this context, BOPET (biaxially oriented polyester film) has attracted much attention due to its excellent mechanical properties, outstanding optical properties, and excellent chemical stability; however, although BOPET performs well in many aspects, it still has certain limitations in terms of barrier properties; therefore, the development of a modified BOPET transparent high-barrier composite film is of great practical significance. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems and to design a modified BOPET transparent high-barrier composite film and a preparation method thereof.

[0004] The first aspect of the present invention provides a modified BOPET transparent high-barrier composite film and a preparation method thereof. The modified BOPET transparent high-barrier composite film comprises a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged outside the modified barrier layer.

[0005] Optionally, in a first implementation of the first aspect of the present invention, the modified barrier layer is prepared from nano-silicon dioxide, polyvinyl alcohol, nano-silver and a coupling agent.

[0006] Optionally, in a second implementation of the first aspect of the present invention, the modified barrier layer is composed of the following raw materials in parts by mass: 5-10 parts of nano-silicon dioxide, 10-15 parts of polyvinyl alcohol, 0.5-1 part of nano-silver, and 1-2 parts of coupling agent.

[0007] Optionally, in a third implementation of the first aspect of the present invention, the protective layer is a polyvinylidene chloride coating.

[0008] The second aspect of the present invention provides a method for preparing a modified BOPET transparent high-barrier composite film, the method for preparing the modified BOPET transparent high-barrier composite film comprising the following steps: Step 1: Dry the nano-silicon dioxide and nano-silver separately to remove the moisture therein, dilute the coupling agent, add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed mixer, stir, mix evenly to obtain a mixed powder, add polyvinyl alcohol into deionized water, heat and continue stirring until the polyvinyl alcohol is completely dissolved, and obtain a polyvinyl alcohol solution; Step 2: slowly add the mixed powder into the polyvinyl alcohol solution and stir to fully disperse the mixed powder in the polyvinyl alcohol solution to obtain a modified barrier layer coating, and use a coating machine to evenly coat the modified barrier layer coating on both sides of the BOPET base layer and dry it; Step 3: Spraying a polyvinylidene chloride coating on the outside of the modified barrier layer obtained after drying, and placing the sprayed film in a drying oven for drying again to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

[0009] Optionally, in a first implementation of the second aspect of the present invention, step one specifically includes the following process: The nano-silicon dioxide and nano-silver are dried separately at a temperature of 80-100° C. and a drying time of 2-4 hours; Use ethanol to dilute the coupling agent, and the dilution ratio of the coupling agent to ethanol is 1:3-1:5; Add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed stirrer at a speed of 2000-3000 rpm for 30-60 minutes to obtain a mixed powder; Add polyvinyl alcohol to deionized water in a mass ratio of 1:5-1:8, heat to 80-90° C., and continue stirring until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution.

[0010] Optionally, in a second implementation of the second aspect of the present invention, step 2 specifically includes the following process: Slowly adding the mixed powder into the polyvinyl alcohol solution, stirring at a speed of 500-1000 rpm for 1-2 hours, so that the mixed powder is fully dispersed in the polyvinyl alcohol solution to obtain a modified barrier layer coating; The modified barrier layer coating is evenly coated on both sides of the BOPET base layer using a coating machine, the coating speed of the coating machine is 10-20 m / min, and the coating thickness is 1-2 μm; The coated film is placed in a drying oven for drying at a temperature of 60-80°C for 1-2 hours to evaporate the water in the modified barrier layer coating and form a firm modified barrier layer.

[0011] Optionally, in a third implementation of the second aspect of the present invention, step three specifically includes the following process: The modified barrier layer obtained after drying is coated with a polyvinylidene chloride coating by spraying, with a spraying pressure of 0.3-0.5 MPa and a spraying thickness of 0.5-1 micron.

[0012] The sprayed film is placed in a drying oven again for drying at a temperature of 40-60° C. for a drying time of 0.5-1 hour to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

[0013] The modified BOPET transparent high-barrier composite film of the present invention has the following advantages: 1. By setting a modified barrier layer on the base layer of BOPET film, the overall barrier performance of the film is significantly improved, effectively blocking the penetration of oxygen, water vapor and other harmful gases, thereby greatly extending the shelf life and preservation effect of the products in the film packaging; 2. During the manufacturing process of the film, nano-silicon dioxide and nano-silver are added to enhance the antibacterial properties of the film, enabling it to effectively inhibit the growth and reproduction of bacteria. At the same time, the addition of nano-silver also significantly improves the ultraviolet blocking ability of the film, protecting the products in the package from damage by ultraviolet rays; 3. In order to further improve the barrier properties and chemical corrosion resistance of the film, the present invention uses a polyvinylidene chloride coating as a protective layer. This coating not only enhances the physical strength of the film, but also enables it to show excellent protective effects when facing corrosion by various chemical substances, ensuring the stability and reliability of the film in harsh environments; 4. The preparation method adopted in the present invention is simple and easy, and the operation steps are clear and straightforward, which is very suitable for application in large-scale production. This makes the film product not only technically advantageous, but also highly operable and economical in the actual production process, greatly reducing production costs and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0015] Figure 1 A schematic diagram of a process example of a method for preparing a modified BOPET transparent high-barrier composite film provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0017] The present invention will now be further described in conjunction with specific embodiments. The following embodiments are intended to illustrate the present invention rather than to further limit the present invention.

[0018] A modified BOPET transparent high-barrier composite film comprises a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged on the outside of the modified barrier layer; the modified barrier layer is composed of the following raw materials in parts by mass: 5-10 parts of nano silicon dioxide, 10-15 parts of polyvinyl alcohol, 0.5-1 part of nano silver, and 1-2 parts of a coupling agent; the protective layer is a polyvinylidene chloride coating.

[0019] As the basic support layer of the composite film, the BOPET base layer has excellent mechanical properties, optical properties and chemical stability. It provides a solid structural framework for the entire composite film and can withstand certain stretching, bending and external pressure to ensure that the composite film maintains a good shape and integrity in various application scenarios; the modified barrier layer arranged on both sides of the BOPET base layer is a key component for achieving high barrier performance, which can effectively prevent the erosion of external factors such as oxygen, water vapor, and ultraviolet rays on internal items. The addition of nano-silicon dioxide gives the modified barrier layer excellent barrier performance and stability. Nano-silicon dioxide has an extremely small particle size and a huge specific surface area, and can form a tight structure in the film to prevent the penetration of gas and water vapor. At the same time, nano-silicon dioxide can also enhance the hardness and wear resistance of the film, improving The utility model relates to a novel composite film having a plurality of nano-silver films and a plurality of nano-silver films. The composite film has ... It can improve the interfacial bonding force between nano-silicon dioxide, nano-silver, etc. and polyvinyl alcohol, and improve the overall performance of the composite film. The selection and use of the coupling agent need to be optimized according to the specific raw materials and application requirements to ensure the best effect; the protective layer arranged on the outside of the modified barrier layer is a polyvinylidene chloride coating. Polyvinylidene chloride has extremely high barrier properties and can further block the penetration of oxygen, water vapor and other harmful substances. At the same time, the polyvinylidene chloride coating also has good chemical corrosion resistance, heat resistance and wear resistance, which can protect the modified barrier layer from the influence of the external environment and extend the service life of the composite film.

[0020] like Figure 1 As shown, a method for preparing a modified BOPET transparent high-barrier composite film comprises the following steps: Step 1: Dry the nano-silicon dioxide and nano-silver separately to remove the moisture therein, dilute the coupling agent, add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed mixer, stir, mix evenly to obtain a mixed powder, add polyvinyl alcohol into deionized water, heat and continue stirring until the polyvinyl alcohol is completely dissolved, and obtain a polyvinyl alcohol solution; Step 2: slowly add the mixed powder into the polyvinyl alcohol solution and stir to fully disperse the mixed powder in the polyvinyl alcohol solution to obtain a modified barrier layer coating, and use a coating machine to evenly coat the modified barrier layer coating on both sides of the BOPET base layer and dry it; Step 3: Spraying a polyvinylidene chloride coating on the outside of the modified barrier layer obtained after drying, and placing the sprayed film in a drying oven for drying again to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

[0021] Step 1 specifically includes the following processes: The nano-silicon dioxide and nano-silver are dried separately at a temperature of 80-100° C. and a drying time of 2-4 hours; Use ethanol to dilute the coupling agent, and the dilution ratio of the coupling agent to ethanol is 1:3-1:5; Add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed stirrer at a speed of 2000-3000 rpm for 30-60 minutes to obtain a mixed powder; Add polyvinyl alcohol to deionized water in a mass ratio of 1:5-1:8, heat to 80-90° C., and continue stirring until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution.

[0022] Step 2 specifically includes the following processes: Slowly adding the mixed powder into the polyvinyl alcohol solution, stirring at a speed of 500-1000 rpm for 1-2 hours, so that the mixed powder is fully dispersed in the polyvinyl alcohol solution to obtain a modified barrier layer coating; The modified barrier layer coating is evenly coated on both sides of the BOPET base layer using a coating machine, the coating speed of the coating machine is 10-20 m / min, and the coating thickness is 1-2 μm; The coated film is placed in a drying oven for drying at a temperature of 60-80°C for 1-2 hours to evaporate the water in the modified barrier layer coating and form a firm modified barrier layer.

[0023] Step 3 specifically includes the following processes: The modified barrier layer obtained after drying is coated with a polyvinylidene chloride coating by spraying, with a spraying pressure of 0.3-0.5 MPa and a spraying thickness of 0.5-1 micron.

[0024] The sprayed film is placed in a drying oven again for drying at a temperature of 40-60° C. for a drying time of 0.5-1 hour to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

[0025] Embodiment 1: A modified BOPET transparent high-barrier composite film, comprising a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged outside the modified barrier layer; The raw material composition of the modified barrier layer: 5 parts of nano-silicon dioxide, 10 parts of polyvinyl alcohol, 0.5 parts of nano-silver, and 1 part of coupling agent; Protective layer: polyvinylidene chloride coating, thickness of 0.5 micron; Preparation method of modified BOPET transparent high barrier composite film: The nano-silicon dioxide and nano-silver were dried in a drying oven at 80°C for 3 hours, the coupling agent was diluted with ethanol, the dilution ratio of the coupling agent to the ethanol was 1:4, the dried nano-silicon dioxide, nano-silver and the diluted coupling agent were added to a high-speed stirrer, and stirred at a speed of 2500 rpm for 45 minutes to obtain a mixed powder; polyvinyl alcohol was added to deionized water, the mass ratio of polyvinyl alcohol to water was 1:6, heated to 85°C and continuously stirred until the polyvinyl alcohol was completely dissolved to obtain a polyvinyl alcohol solution; the mixed powder was slowly added to the polyvinyl alcohol solution, and stirred at a speed of 800 rpm for 1.5 hours to obtain a modified barrier layer coating; The modified barrier layer coating was evenly coated on both sides of the BOPET base layer using a precision coating machine at a coating speed of 15 m / min and a coating thickness of 1.5 μm, and then placed in a drying oven at 70°C for 1.5 hours. The polyvinylidene chloride coating was sprayed on the outside of the modified barrier layer at a spraying pressure of 0.4 MPa, and finally placed in a drying oven at 50°C for 0.8 hours.

[0026] Embodiment 2: A modified BOPET transparent high-barrier composite film, comprising a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged outside the modified barrier layer; The raw material composition of the modified barrier layer: 8 parts of nano-silicon dioxide, 13 parts of polyvinyl alcohol, 0.8 parts of nano-silver, and 1.5 parts of coupling agent; Protective layer: polyvinylidene chloride coating, thickness of 0.8 microns; Preparation method of modified BOPET transparent high barrier composite film: The nano-silicon dioxide and nano-silver were dried in a drying oven at 90°C for 2.5 hours; the coupling agent was diluted with ethanol, and the dilution ratio was 1:3.5 of coupling agent to ethanol; the dried nano-silicon dioxide, nano-silver and diluted coupling agent were added into a high-speed mixer, and stirred at a speed of 2800 rpm for 50 minutes to obtain a mixed powder; polyvinyl alcohol was added into deionized water, and the mass ratio of polyvinyl alcohol to water was 1:7, and the mixture was heated to 88°C and stirred continuously until the polyvinyl alcohol was completely dissolved to obtain a polyvinyl alcohol solution; the mixed powder was slowly added into the polyvinyl alcohol solution, and stirred at a speed of 900 rpm for 1.2 hours to obtain a modified barrier layer coating.

[0027] The modified barrier layer coating was evenly coated on both sides of the BOPET base layer using a precision coating machine at a coating speed of 18 m / min and a coating thickness of 1.8 μm, and then placed in a drying oven at 75°C for 1.2 hours. The polyvinylidene chloride coating was sprayed on the outside of the modified barrier layer at a spraying pressure of 0.45 MPa, and finally placed in a drying oven at 55°C for 0.7 hours.

[0028] Embodiment 3: A modified BOPET transparent high-barrier composite film, comprising a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged outside the modified barrier layer; The raw material composition of the modified barrier layer: 10 parts of nano-silicon dioxide, 15 parts of polyvinyl alcohol, 1 part of nano-silver, and 2 parts of coupling agent; Protective layer: polyvinylidene chloride coating, thickness of 1 micron; Preparation method of modified BOPET transparent high barrier composite film: The nano-silicon dioxide and nano-silver were dried in a drying oven at 95°C for 2 hours, the coupling agent was diluted with ethanol in a dilution ratio of 1:3 between the coupling agent and ethanol, the dried nano-silicon dioxide, nano-silver and the diluted coupling agent were added into a high-speed mixer, and stirred at a speed of 3000 rpm for 60 minutes to obtain a mixed powder; polyvinyl alcohol was added into deionized water in a mass ratio of polyvinyl alcohol to water of 1:8, heated to 90°C and continuously stirred until the polyvinyl alcohol was completely dissolved to obtain a polyvinyl alcohol solution; the mixed powder was slowly added into the polyvinyl alcohol solution, and stirred at a speed of 1000 rpm for 1 hour to obtain a modified barrier layer coating.

[0029] The modified barrier layer coating was evenly coated on both sides of the BOPET base layer using a precision coating machine at a coating speed of 20 m / min and a coating thickness of 2 μm, and then placed in a drying oven at 80°C for 1 hour. The polyvinylidene chloride coating was sprayed on the outside of the modified barrier layer at a spraying pressure of 0.5 MPa, and finally placed in a drying oven at 60°C for 0.5 hour.

[0030] The performance tests were conducted on the modified BOPET transparent high barrier composite films prepared in the three embodiments and the ordinary BOPET film of the comparative example. The results are shown in the following table: Performance Indicators Example 1 Example 2 Example 3 Comparative example (ordinary BOPET film) Oxygen permeability (cm³ / m²・d・atm) 4.5 4.2 4 50 Water vapor transmission rate (g / m²・d) 2.8 2.5 2 10 Antimicrobial properties Good, can significantly inhibit bacterial growth Good, has a strong inhibitory effect on bacterial growth Good, outstanding antibacterial effect No antibacterial properties UV blocking rate (%) 91 93 95 50 1. Oxygen permeability test: Use a high-precision oxygen permeability tester, set the test environment temperature to 25℃±2℃, and control the relative humidity to 50%±5%. Install the film sample to be tested flatly in the test chamber of the tester, ensure that the sample and the test chamber are well sealed and there is no oxygen leakage. Turn on the tester to allow a certain pressure of oxygen to flow on one side of the film, while the other side maintains a lower oxygen partial pressure. Use the sensor to monitor the changes in oxygen concentration on both sides of the film in real time, and calculate the amount of oxygen permeated per unit area of ​​the film per unit time according to the test time and the area of ​​the film, in units of cm³ / m²・d・atm. During the test, in order to ensure the accuracy of the test results, repeat the test for many times, and take the average value as the final oxygen permeability result; 2. Water vapor transmission rate test: Use a water vapor transmission rate tester, set the test environment temperature to 38℃±1℃, and the relative humidity to 90%±2%, simulate the common high humidity environment conditions, clamp the film sample between the test chambers of the tester, ensure that the sample is sealed without leakage, let the water vapor exist at a certain humidity and pressure on one side of the film, and keep the other side dry. The tester monitors the amount of water vapor passing through the film through the sensor, and determines the amount of water vapor permeated per unit area of ​​the film per unit time according to the test time and film area, in units of g / m²・d. Similarly, in order to improve the reliability of the test results, multiple tests are carried out and the average value is taken; 3. Antibacterial performance test: select common bacterial strains, such as Escherichia coli, Staphylococcus aureus, etc. as test strains, cut the film sample into a square of a certain size, put it in a sterile culture dish, add an appropriate amount of culture solution containing bacterial strains to the culture dish, make the film sample fully contact with the bacteria, then place the culture dish in a constant temperature incubator, set the temperature to 37℃±1℃, and culture for a certain time, usually 24 hours or 48 hours. After the culture is completed, the colony counting method is used for testing. The specific method is: take out the film sample from the culture dish, rinse the sample surface with sterile saline to remove the unabsorbed bacteria. Then dilute the rinse solution, spread it on the nutrient agar plate, and place it in the incubator for further culture. After the colony growth is stable, count the colonies, and evaluate the antibacterial performance of the film by comparing the changes in the number of bacteria before and after contact with the film. In addition, the antibacterial effect of the film can be further verified by measuring the absorbance changes of the bacterial culture solution before and after contact with the film. 4. UV blocking rate test: Use a UV spectrophotometer and set the test wavelength range to 200nm-400nm, covering the main wavelength area of ​​ultraviolet rays. Place the film sample in the sample chamber of the spectrophotometer to ensure that the light passes through the film vertically. Measure the light intensity of ultraviolet rays of different wavelengths without and with film blocking. Calculate the transmittance of the film to ultraviolet rays of different wavelengths based on the measurement results. Then, calculate the UV blocking rate using the following formula: UV blocking rate = (1-transmittance) × 100%, expressed as a percentage. To ensure the accuracy of the test results, test film samples at multiple different locations and take the average value as the final UV blocking rate result. At the same time, further study the UV blocking performance of the film under different conditions by changing the incident angle of ultraviolet rays.

[0031] It can be seen from the above test results that the modified BOPET transparent high-barrier composite film of the present invention has excellent barrier properties, antibacterial properties and ultraviolet blocking capabilities; In terms of barrier properties: the oxygen permeability and water vapor permeability of the modified BOPET transparent high-barrier composite films in the three examples are much lower than those of ordinary BOPET films, which shows that the barrier properties of the films are effectively improved by adding nano-silicon dioxide, polyvinyl alcohol, nano-silver and setting polyvinylidene chloride coating, which can better protect the items in the package from erosion by oxygen and water vapor; In terms of antibacterial properties: the films of Examples 1-3 all exhibit good antibacterial properties, while ordinary BOPET films have no antibacterial properties. This is because the addition of nanosilver gives the modified films antibacterial functions, which can inhibit the growth and reproduction of bacteria, and is of great significance in packaging applications in the fields of food, medicine, etc. In terms of UV blocking rate: the UV blocking rate of the films in the three embodiments is significantly higher than that of ordinary BOPET films. The synergistic effect of nano-silicon dioxide and nano-silver enhances the film's ability to block UV rays, which can protect the items in the package from damage by UV rays and extend the shelf life and service life of the products. It can be seen from the performance tests of the three embodiments that the modified BOPET transparent high-barrier composite film proposed in the present invention has excellent performance in terms of barrier performance, antibacterial performance and ultraviolet blocking ability, and has broad application prospects. Compared with ordinary BOPET film, the modified composite film can better meet the demand of modern packaging industry for high-performance packaging materials; by arranging the modified barrier layer on both sides of the BOPET base layer, the barrier performance of the film is improved, and the penetration of oxygen, water vapor, etc. is effectively blocked; the addition of nano-silicon dioxide and nano-silver enhances the antibacterial performance and ultraviolet blocking ability of the film; the polyvinylidene chloride coating is used as a protective layer to further improve the barrier performance and chemical corrosion resistance of the film; the preparation method of the present invention is simple, easy to operate, and suitable for large-scale production.

[0032] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A modified BOPET transparent high barrier composite film, characterized in that: The modified BOPET transparent high-barrier composite film comprises a BOPET base layer, a modified barrier layer arranged on both sides of the BOPET base layer, and a protective layer arranged outside the modified barrier layer.

2. A modified BOPET transparent high barrier composite film as claimed in claim 1, characterized in that: The modified barrier layer is prepared from nano silicon dioxide, polyvinyl alcohol, nano silver and a coupling agent.

3. A modified BOPET transparent high barrier composite film as claimed in claim 2, characterized in that: The modified barrier layer is composed of the following raw materials in parts by mass: 5-10 parts of nano silicon dioxide, 10-15 parts of polyvinyl alcohol, 0.5-1 parts of nano silver, and 1-2 parts of a coupling agent.

4. A modified BOPET transparent high barrier composite film according to claim 1, characterized in that: The protective layer is a polyvinylidene chloride coating.

5. A method for preparing a modified BOPET transparent high-barrier composite film, characterized in that: The method for preparing the modified BOPET transparent high-barrier composite film comprises the following steps: Step 1: Dry the nano-silicon dioxide and nano-silver separately to remove the moisture therein, dilute the coupling agent, add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed mixer, stir, mix evenly to obtain a mixed powder, add polyvinyl alcohol into deionized water, heat and continue stirring until the polyvinyl alcohol is completely dissolved, and obtain a polyvinyl alcohol solution; Step 2: slowly add the mixed powder into the polyvinyl alcohol solution and stir to fully disperse the mixed powder in the polyvinyl alcohol solution to obtain a modified barrier layer coating, and use a coating machine to evenly coat the modified barrier layer coating on both sides of the BOPET base layer and dry it; Step 3: Spraying a polyvinylidene chloride coating on the outside of the modified barrier layer obtained after drying, and placing the sprayed film in a drying oven for drying again to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

6. The method for preparing a modified BOPET transparent high-barrier composite film according to claim 5, characterized in that: Step 1 specifically includes the following processes: The nano-silicon dioxide and nano-silver are dried separately at a temperature of 80-100° C. and a drying time of 2-4 hours; Use ethanol to dilute the coupling agent, and the dilution ratio of the coupling agent to ethanol is 1:3-1:5; Add the pretreated nano-silicon dioxide, nano-silver and the diluted coupling agent into a high-speed stirrer at a speed of 2000-3000 rpm for 30-60 minutes to obtain a mixed powder; Add polyvinyl alcohol to deionized water in a mass ratio of 1:5-1:8, heat to 80-90° C., and continue stirring until the polyvinyl alcohol is completely dissolved to obtain a polyvinyl alcohol solution.

7. The method for preparing a modified BOPET transparent high-barrier composite film according to claim 5, characterized in that: Step 2 specifically includes the following processes: Slowly adding the mixed powder into the polyvinyl alcohol solution, stirring at a speed of 500-1000 rpm for 1-2 hours, so that the mixed powder is fully dispersed in the polyvinyl alcohol solution to obtain a modified barrier layer coating; The modified barrier layer coating is evenly coated on both sides of the BOPET base layer using a coating machine, the coating speed of the coating machine is 10-20 m / min, and the coating thickness is 1-2 μm; The coated film is placed in a drying oven for drying at a temperature of 60-80°C for 1-2 hours to evaporate the water in the modified barrier layer coating and form a firm modified barrier layer.

8. The method for preparing a modified BOPET transparent high-barrier composite film according to claim 5, wherein step three specifically comprises the following process: The modified barrier layer obtained after drying is coated with a polyvinylidene chloride coating by spraying, with a spraying pressure of 0.3-0.5 MPa and a spraying thickness of 0.5-1 micron.

9. The sprayed film is placed in a drying oven again for drying at a temperature of 40-60°C for 0.5-1 hour to dry and solidify the polyvinylidene chloride coating to obtain a modified BOPET transparent high-barrier composite film.

Images