Recyclable PET composite cover film and preparation method thereof

Abstract

The invention discloses a recoverable PET composite cover film and a preparation method thereof, and relates to the technical field of PET heat-sealing materials. The recyclable PET composite cover film comprises a PET composite film as well as an isolation part and an adhesive layer which are arranged on the surface of the composite film, wherein the height of the isolation part is greater than the thickness of the adhesive layer. Wherein the adhesive layer is made of a composite adhesive; the PET composite film is prepared by compounding a PET thin film and a barrier film; the barrier film is any one of a PET film, a VMPET film and an alumina-plated PET film. The introduction of the composite adhesive prepared from raw materials such as bio-based polylactic acid glycol, hydroxylated silicon dioxide and an end-capped prepolymer effectively improves the composite strength, recoverability and thermal stability of the PET composite cover film; the introduction of the isolation part at the end far away from the PET composite film improves the inter-film adsorption resistance of the PET composite cover film. Therefore, the method has a wider application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of PET heat-sealing materials, and in particular to a recyclable PET composite cover film and a preparation method thereof. Background Art

[0002] PET's molecular structure is highly symmetrical, with a certain degree of crystallization orientation. A milky white or light yellow, highly crystalline polymer, PET has a smooth and lustrous surface, excellent creep resistance, fatigue resistance, and friction resistance, low wear and high hardness, and possesses the highest toughness among thermoplastics. It also offers excellent electrical insulation, minimal temperature effects, is non-toxic, weather-resistant, chemically stable, and resistant to weak acids and organic solvents. Therefore, it is widely used in fibers, films, packaging materials, and other fields.

[0003] With growing environmental awareness and the need for recyclability, modified heat-sealable PET is being used for the inner film. To reduce costs, the industry is reducing the thickness of heat-sealable PET. However, due to factors such as the high price and low heat-seal strength of heat-sealable PET, gluing has become a new option. This not only saves costs but also achieves a heat-seal strength of ≥12.0N / 15mm. When used with sheet materials, it can be torn without delamination and exhibits excellent tear resistance. If the product requires light protection and privacy, VMPET can be used as the middle layer. If the product needs to be visible to consumers while also requiring moisture and oxygen resistance, aluminum oxide-coated PET can be used as the middle layer.

[0004] However, in practice, PET composite cover films still suffer from issues such as adhesive residue remaining on the PET film surface during recycling, which can reduce the PET's tensile strength, leading to poor recyclability. Furthermore, the PET composite cover films suffer from insufficient composite strength after heat sealing, low peel strength, and interlayer adsorption after winding. Therefore, the composite strength, recyclability, and interlayer adsorption resistance of existing PET composite cover films still need to be improved. Summary of the Invention

[0005] The purpose of the present invention is to provide a recyclable PET composite cover film and a preparation method thereof, to solve the following technical problems:

[0006] The existing PET composite cover film still has problems such as low composite strength, recyclability, and poor anti-adsorption ability between films.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A recyclable PET composite cover film, comprising a PET composite film and an isolation portion and an adhesive layer provided on the surface of the composite film;

[0009] The adhesive layer is made of a composite adhesive;

[0010] The preparation method of the composite adhesive comprises the following steps:

[0011] Hydroxylated silica is added to bio-based polylactic acid diol and ultrasonically dispersed for 30-50 minutes. The mixture is then added to the end-capped prepolymer and stirred at 78-82°C for 1-1.5 hours. Dimethylol propionic acid is then added and the temperature is raised to 88-90°C for reaction for 1.5-2 hours. The mixture is cooled to 35-45°C and triethylamine is added. Deionized water is then added under stirring. The mixture is emulsified for 30-40 minutes, sealed, and aged at 43-47°C for 20-25 hours to obtain a composite adhesive.

[0012] Preferably, the mass ratio of the bio-based polylactic acid diol, hydroxylated silica, end-capped prepolymer, dimethylol propionic acid, triethylamine, and deionized water is 8-15:5-10:45-65:3-5:4-5:40-60.

[0013] Preferably, the preparation method of the hydroxylated silicon dioxide is as follows:

[0014] Nano-silica is added to anhydrous toluene and ultrasonically treated for 30-50 minutes. Then, 3-aminopropyltriethoxysilane is added and refluxed for 6-12 hours under a nitrogen atmosphere. After cooling, the mixture is centrifuged and the precipitate is washed. The mixture is then dispersed in deionized water. A hydrogen peroxide solution is added, and the mixture is stirred at 55-60° C. for 4-5 hours, followed by centrifugation, washing the precipitate, vacuum drying, and sieving to obtain hydroxylated silica.

[0015] Preferably, the usage ratio of anhydrous toluene, nano-silica, 3-aminopropyltriethoxysilane, deionized water, and hydrogen peroxide is 100-150 mL: 5-10 g: 0.5-1 g: 50 mL: 1-2 mL;

[0016] The mass fraction of the hydrogen peroxide aqueous solution is 30%.

[0017] Preferably, the preparation method of the end-capped prepolymer is as follows:

[0018] Polyethylene adipate is dehydrated at 100-120° C. and a vacuum degree of -0.09 MPa for 2-3 hours, cooled to 78-82° C., and then isocyanate and dibutyltin dilaurate are added and reacted for 2-3 hours to obtain a capped prepolymer.

[0019] Preferably, the mass ratio of polyethylene adipate, isocyanate and dibutyltin dilaurate is 30-40:15-25:0.1-0.3.

[0020] Preferably, the PET composite film is made by compounding a PET film and a barrier film; the barrier film is any one of a PET film, a VMPET film, and an alumina-coated PET film.

[0021] A method for preparing a recyclable PET composite cover film comprises the following steps:

[0022] S1: Compounding the PET film and the barrier film through a dry compounding process to obtain a PET composite film;

[0023] S2: An adhesive layer and a spacer are provided on the surface of the PET composite film, followed by hot air drying at 60-80°C, and finally winding the film to obtain a recyclable PET composite cover film.

[0024] Preferably, the adhesive amount of the composite adhesive in the adhesive layer in S2 is 5-6 g / m 2 ;

[0025] The end of the isolation portion far from the PET composite film in S2 is coated with a sticky material.

[0026] Preferably, the viscous material is any one of a composite adhesive and a water-based polyurethane adhesive.

[0027] Preferably, the winding tension during the winding process in S2 is 50-80N.

[0028] Beneficial effects of the present invention:

[0029] The present invention provides a recyclable PET composite cover film and a preparation method thereof. The present invention effectively improves the composite strength, recyclability, temperature resistance and anti-inter-film adsorption capability of the PET composite cover film through the following method.

[0030] (1) During the preparation of the composite adhesive of the present invention, hydroxylated silica is evenly distributed in the adhesive system after ultrasonic dispersion. The abundant hydroxyl groups on its surface can react chemically with the isocyanate groups in the polyurethane prepolymer to form an "inorganic-organic" cross-linked network, which can improve the cohesive strength of the adhesive; the "physical reinforcement effect" of the nanoparticles can also increase the interfacial bonding force between the adhesive layer and the substrate, thereby significantly improving the peel strength. The uniform dispersion of silica can reduce the residue of the adhesive during the recycling process, which is beneficial to the clean separation of the PET film and indirectly improves the recycling efficiency. The high thermal stability of silica can serve as a "heat-resistant skeleton" to inhibit the molecular chain movement of the adhesive at high temperatures and delay softening or decomposition; when the adhesive is subjected to high temperatures, the cross-linked structure of hydroxylated silica and the polyurethane network can maintain the mechanical properties of the adhesive layer, reducing the decrease in peel strength or failure of the adhesive layer due to thermal expansion.

[0031] (2) In the preparation process of the composite adhesive of the present invention, bio-based polylactic acid diol is used as an oligomer polyol. The lactic acid structural unit in its molecular chain gives the adhesive a certain flexibility, which can absorb energy through the extension of the molecular chain during the peeling process, thereby avoiding brittle fracture of the adhesive layer. When compounded with rigid hydroxylated silica and polyurethane prepolymer, a "rigid and flexible" network structure can be formed, which improves the ductility during peeling while maintaining strength, thereby optimizing the peeling strength. Bio-based polylactic acid diol has the dual characteristics of biodegradability and thermal stability. During the PET recycling process, the polylactic acid chain segment can be partially degraded into small molecules under high temperature or alkaline conditions, avoiding remaining in the PET recycled material in the form of large molecules. At the same time, its degradation products have little effect on the performance of PET, which is beneficial to improving the purity and reprocessability of the recycled PET. Polylactic acid diol forms a cross-linked structure by reacting with isocyanate, and its temperature resistance can be improved by the cross-linking density of the polyurethane network. In addition, after being compounded with hydroxylated silica, the heat-resistant skeleton of the inorganic filler can make up for the insufficient heat resistance of the polylactic acid segment. Under the synergistic effect of the two, the temperature resistance of the adhesive can meet the use requirements. Bio-based polylactic acid diol is a low-volatile liquid, and the aqueous emulsification process is adopted in the preparation process of the composite adhesive of the present invention, using water instead of organic solvent as the dispersion medium, which can greatly reduce VOC emissions. The "rigidity enhancement" of hydroxylated silica and the "flexibility adjustment" of bio-based polylactic acid diol work synergistically, so that the adhesive has both high strength and ductility, can withstand greater tension and is not easy to break when peeled; the high thermal stability of silica and the synergistic effect of the polyurethane-polylactic acid cross-linking network enable the adhesive to maintain structural stability in medium and high temperature environments, avoiding peeling failure caused by thermal softening.

[0032] (3) The height of the isolation part of the present invention is higher than the thickness of the adhesive layer, and is in the shape of a point, diamond, cross, etc. with a prominent thickness. There is a significant height difference with the adhesive layer, which can play a supporting role, thereby solving the adsorption problem between the cover films.

[0033] Therefore, the recyclable PET composite cover film prepared by the present invention has excellent composite strength, recyclability, temperature resistance, anti-inter-film adsorption ability, and broader application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic structural diagram of the recyclable PET composite cover film of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, some of the raw materials used in the following examples and comparative examples of the present invention are as follows:

[0038] Polyethylene adipate (Mn=1000) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., item number: P341826; bio-based polylactic acid diol (Nature Works 2003D) was purchased from Dongguan Kunfu Engineering Plastic Raw Materials Co., Ltd.; water-based polyurethane dispersion CN-115 was purchased from Hefei Konada New Materials Co., Ltd.; water-based polyurethane dispersion CN-116 was purchased from Hefei Konada New Materials Co., Ltd.

[0039] Example 1: A method for preparing a recyclable PET composite cover film is as follows:

[0040] S1: 5 g of nano-silica was added to 100 mL of anhydrous toluene and subjected to ultrasonic treatment at a power of 400 W and a frequency of 30 kHz for 30 min. Then, 0.5 g of 3-aminopropyltriethoxysilane was added and refluxed under a nitrogen atmosphere for 6 h. After cooling to 20°C, the mixture was centrifuged and the precipitate was washed 3 times with toluene and ethanol respectively. The precipitate was then dispersed in 50 mL of deionized water. 1 mL of a 30% aqueous hydrogen peroxide solution was added, and the mixture was stirred at 55°C for 4 h. After centrifugation, the mixture was washed 5 times with deionized water. Finally, the mixture was vacuum dried at 55°C for 20 h and passed through an 80-mesh sieve to obtain hydroxylated silica.

[0041] S2: Dehydrate 30 g of polyethylene adipate at 100° C. and a vacuum degree of -0.09 MPa for 2 h. After cooling to 78° C., add 15 g of isocyanate and 0.1 g of dibutyltin dilaurate and react at 78° C. for 2 h to obtain a capped prepolymer.

[0042] S3: 5 g of hydroxylated silica was added to 8 g of bio-based polylactic acid diol and ultrasonically dispersed at a power of 400 W and a frequency of 30 kHz for 30 minutes. The mixture was then added to 45 g of capped prepolymer and stirred at 78°C for 1 hour. 3 g of dimethylolpropionic acid was then added and the temperature was raised to 88°C for reaction for 1.5 hours. After cooling to 35°C, 4 g of triethylamine was added and 40 g of deionized water was slowly added under stirring at 1800 rpm. The mixture was emulsified at 1800 rpm for 30 minutes, sealed, and aged at 43°C for 20 hours to obtain a composite adhesive.

[0043] S4: combining the PET film with the PET film through a dry lamination process to obtain a two-layered PET composite film;

[0044] S5: Use composite adhesive to set the glue amount to 11g / m at the far end of the PET composite film. 2 The isolation part is then glued with a composite adhesive at a glue amount of 5g / m near the end of the PET composite film. 2 The composite adhesive was applied to the adhesive layer, and then hot air dried at 60 ° C, and finally rolled up with a winding tension of 50N to obtain the attached Figure 1 The recyclable PET composite cover film shown in Figure a.

[0045] Example 2: A method for preparing a recyclable PET composite cover film is as follows:

[0046] S1: 7.5 g of nano-silica was added to 125 mL of anhydrous toluene and subjected to ultrasonic treatment at a power of 500 W and a frequency of 40 kHz for 40 min. Then, 0.8 g of 3-aminopropyltriethoxysilane was added and refluxed under a nitrogen atmosphere for 9 h. After cooling to 25°C, the mixture was centrifuged and washed with toluene and ethanol 4 times each. The precipitate was then dispersed in 50 mL of deionized water. 1.5 mL of a 30% aqueous hydrogen peroxide solution was added. The mixture was stirred at 58°C for 4.5 h, centrifuged, washed with deionized water 6 times, and finally dried in vacuo at 58°C for 23 h and passed through a 90-mesh sieve to obtain hydroxylated silica.

[0047] S2: Dehydrate 35 g of polyethylene adipate at 110° C. and a vacuum degree of -0.09 MPa for 2.5 h. After cooling to 80° C., add 20 g of isocyanate and 0.2 g of dibutyltin dilaurate and react at 80° C. for 2.5 h to obtain a capped prepolymer.

[0048] S3: 7.5 g of hydroxylated silica was added to 11.5 g of bio-based polylactic acid diol and ultrasonically dispersed at a power of 500 W and a frequency of 40 kHz for 40 minutes. The mixture was then added to 55 g of the capped prepolymer and stirred at 80°C for 1.2 hours. 4 g of dimethylolpropionic acid was then added and the temperature was raised to 89°C for reaction for 1.8 hours. After cooling to 405°C, 4.5 g of triethylamine was added. 50 g of deionized water was slowly added under stirring at 1900 rpm. The mixture was emulsified at 1900 rpm for 35 minutes, sealed, and aged at 45°C for 23 hours to obtain a composite adhesive.

[0049] S4: combining the PET film with the PET film through a dry lamination process to obtain a three-layered PET composite film;

[0050] S5: Set the glue amount of water-based polyurethane dispersion CN-115 at the far end of the PET composite film to 13g / m 2 The isolation part is then glued with a composite adhesive at a glue amount of 5.5g / m near the end of the PET composite film. 2 The composite adhesive was applied to the adhesive layer, and then hot air dried at 70 ° C, and finally rolled up with a winding tension of 65N to obtain the attached Figure 1 The recyclable PET composite cover film shown in Figure b.

[0051] Example 3: A method for preparing a recyclable PET composite cover film is as follows:

[0052] S1: 10 g of nano-silica was added to 150 mL of anhydrous toluene and subjected to ultrasonic treatment at a power of 600 W and a frequency of 50 kHz for 50 min. Then, 1 g of 3-aminopropyltriethoxysilane was added and refluxed under a nitrogen atmosphere for 12 h. After cooling to 35°C, the mixture was centrifuged and the precipitate was washed 5 times with toluene and ethanol respectively. The precipitate was then dispersed in 50 mL of deionized water. 2 mL of a 30% aqueous hydrogen peroxide solution was added. The mixture was stirred at 60°C for 5 h, centrifuged, and washed 7 times with deionized water. Finally, the mixture was vacuum dried at 60°C for 25 h and passed through a 100-mesh sieve to obtain hydroxylated silica.

[0053] S2: Dehydrate 40 g of polyethylene adipate at 120° C. and a vacuum degree of -0.09 MPa for 3 h. After cooling to 82° C., add 25 g of isocyanate and 0.3 g of dibutyltin dilaurate and react at 82° C. for 3 h to obtain a capped prepolymer.

[0054] S3: 10 g of hydroxylated silica was added to 15 g of bio-based polylactic acid diol and ultrasonically dispersed at a power of 600 W and a frequency of 50 kHz for 50 min. The mixture was then added to 65 g of capped prepolymer and stirred at 82°C for 1.5 h. 5 g of dimethylolpropionic acid was then added and the temperature was raised to 90°C for reaction for 2 h. After cooling to 45°C, 5 g of triethylamine was added and 60 g of deionized water was slowly added at a stirring rate of 2000 r / min. The mixture was emulsified at 2000 r / min for 40 min, sealed, and aged at 47°C for 25 h to obtain a composite adhesive.

[0055] S4: combining the PET film with the PET film through a dry lamination process to obtain a 4-layered PET composite film;

[0056] S5: Set the glue amount of aqueous polyurethane dispersion CN-116 at the far end of the PET composite film to 15g / m 2 The isolation part is then glued with a composite adhesive at a glue amount of 6g / m near the end of the PET composite film. 2The composite adhesive was set to a glue amount of 1 layer, and then hot air drying was performed at 80°C, and finally winding was performed at a winding tension of 80N to obtain the attached Figure 1 The recyclable PET composite cover film shown in Figure c.

[0057] Comparative Example 1:

[0058] Compared with Example 1, this comparative example only replaces the "hydroxylated silicon dioxide" added in the preparation process of S3 with "nano-silica", and the remaining steps and parameters are the same, which will not be repeated in this comparative example. Finally, a recyclable PET composite cover film is obtained.

[0059] Comparative Example 2:

[0060] Compared with Example 1, this comparative example only does not add "hydroxylated silicon dioxide" during the preparation of S3. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a recyclable PET composite cover film is obtained.

[0061] Comparative Example 3:

[0062] This comparative example is compared with Example 1 except that "bio-based polylactic acid diol and hydroxylated silica" are not added during the preparation of S3. The remaining steps and parameters are the same and will not be repeated in this comparative example. Finally, a recyclable PET composite cover film is obtained;

[0063] Comparative Example 4:

[0064] Compared with Example 1, this comparative example only changes the step of "setting the glue amount of the composite adhesive at the far end of the PET composite film to 11g / m2" in the preparation process of S5. 2 The isolation part is replaced by "using composite adhesive at the far end of the PET composite film to set the glue amount to 5g / m 2 The remaining steps and parameters are the same and will not be repeated in this comparative example, and finally a recyclable PET composite cover film is obtained.

[0065] Comparative Example 5:

[0066] Compared with Example 1, this comparative example does not include the following steps in the preparation process of S5: "setting the glue amount of 11g / m2 with composite adhesive at the far end of the PET composite film" 2 The remaining steps and parameters are the same and will not be repeated in this comparative example, and finally a recyclable PET composite cover film is obtained.

[0067] Performance testing:

[0068] Determination of peel strength:

[0069] With reference to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes," the peel strength (N / 15 mm) between the printed PET film and the composite adhesive in the recyclable PET composite cover films prepared in Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention was measured. The results are shown in Table 1.

[0070] Determination of recovery performance:

[0071] The recyclable PET composite cover films prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 were soaked in a 5% sodium hydroxide solution at 80°C for 30 minutes, and then the residual adhesive amount (mg / cm 2 ) and the tensile strength retention rate of recycled PET (%), the measurement results are shown in Table 1;

[0072] Determination of temperature resistance:

[0073] The recyclable PET composite cover films prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 were subjected to a -20°C-80°C cycle for 5 times, after which they were inspected for cracking; and the adhesive layer was inspected for yellowing after heat sealing at 120°C. The test results are shown in Table 1.

[0074] Determination of adsorption:

[0075] The recyclable PET composite cover films prepared in Examples 1 to 3 of the present invention and Comparative Examples 4 and 5 were observed to see whether they would adsorb each other after being rolled up. The measurement results are shown in Table 1.

[0076] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-5

[0077]

[0078] Data Analysis:

[0079] As can be seen from Table 1, the recyclable PET composite cover film prepared in the embodiment of the present invention has excellent composite strength, recyclability, temperature resistance, and anti-inter-film adsorption ability.

[0080] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A recyclable PET composite cover film, characterized in that: The recyclable PET composite cover film comprises a PET composite film and an isolation portion and an adhesive layer provided on the surface of the composite film, wherein the height of the isolation portion is greater than the thickness of the adhesive layer; The adhesive layer is made of a composite adhesive; The preparation method of the composite adhesive comprises the following steps: Hydroxylated silica is added to bio-based polylactic acid diol and ultrasonically dispersed for 30-50 minutes. The mixture is then added to the end-capped prepolymer and stirred at 78-82°C for 1-1.5 hours. Dimethylol propionic acid is then added and the temperature is raised to 88-90°C for reaction for 1.5-2 hours. The mixture is cooled to 35-45°C and triethylamine is added. Deionized water is then added under stirring. The mixture is emulsified for 30-40 minutes, sealed, and aged at 43-47°C for 20-25 hours to obtain a composite adhesive.

2. The recyclable PET composite covering film according to claim 1, characterized in that: The mass ratio of the bio-based polylactic acid diol, hydroxylated silica, end-capped prepolymer, dihydroxymethylpropionic acid, triethylamine and deionized water is 8-15:5-10:45-65:3-5:4-5:40-60.

3. The recyclable PET composite covering film according to claim 1, characterized in that: The preparation method of the hydroxylated silicon dioxide is as follows: Nano-silica is added to anhydrous toluene and ultrasonically treated for 30-50 minutes. Then, 3-aminopropyltriethoxysilane is added and refluxed for 6-12 hours under a nitrogen atmosphere. After cooling, the mixture is centrifuged and the precipitate is washed. The mixture is then dispersed in deionized water. A hydrogen peroxide solution is added, and the mixture is stirred at 55-60° C. for 4-5 hours, followed by centrifugation, washing the precipitate, vacuum drying, and sieving to obtain hydroxylated silica.

4. The recyclable PET composite covering film according to claim 3, characterized in that: The usage ratio of anhydrous toluene, nano-silica, 3-aminopropyltriethoxysilane, deionized water, and hydrogen peroxide is 100-150 mL: 5-10 g: 0.5-1 g: 50 mL: 1-2 mL; The mass fraction of the hydrogen peroxide aqueous solution is 30%.

5. The recyclable PET composite covering film according to claim 1, characterized in that: The preparation method of the end-capped prepolymer is as follows: Polyethylene adipate is dehydrated at 100-120° C. and a vacuum degree of -0.09 MPa for 2-3 hours, cooled to 78-82° C., and then isocyanate and dibutyltin dilaurate are added and reacted for 2-3 hours to obtain a capped prepolymer.

6. The recyclable PET composite covering film according to claim 5, characterized in that: The mass ratio of the polyethylene adipate, isocyanate and dibutyltin dilaurate is 30-40:15-25:0.1-0.

3.

7. The recyclable PET composite covering film according to claim 1, characterized in that: The PET composite film is prepared by compounding a PET film and a barrier film; the barrier film is any one of a PET film, a VMPET film, and an alumina-coated PET film.

8. A method for preparing the recyclable PET composite cover film according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1: Compounding the PET film and the barrier film through a dry compounding process to obtain a PET composite film; S2: An adhesive layer and a spacer are provided on the surface of the PET composite film, followed by hot air drying at 60-80°C, and finally winding the film to obtain a recyclable PET composite cover film.

9. The method for preparing the recyclable PET composite cover film according to claim 8, characterized in that: The adhesive amount of the composite adhesive in the adhesive layer of S2 is 5-6 g / m 2 ; The end of the isolation portion far from the PET composite film in S2 is coated with a sticky material.

10. The method for preparing the recyclable PET composite cover film according to claim 8, characterized in that: The winding tension during the winding process in S2 is 50-80N.

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