Paper-plastic sealing film as well as preparation method and application thereof

Abstract

The invention provides a paper-plastic sealing film as well as a preparation method and application thereof, and relates to the technical field of sealing films. The preparation method of the paper-plastic sealing film comprises the following steps: S1, coating one side of the paper base layer with a single-component polyurethane adhesive to form a first bonding layer, and carrying out primary compounding, rolling and primary curing on the printing layer and the first bonding layer; s2, the other side of the paper base layer is coated with a single-component polyurethane adhesive to form a second bonding layer, and the polyester film layer and the second bonding layer are composited for the second time, rolled and cured for the second time; and S3, coating the non-compounded side of the polyester film layer with the bi-component polyurethane adhesive to form a third bonding layer, compounding the polyolefin film and the third bonding layer for the third time, rolling, and curing for the third time. The flatness of the paper-plastic sealing film is remarkably improved, the composite strength is excellent, layering is avoided, and bubbles are avoided after heat sealing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sealing film, in particular to a paper-plastic sealing film and a preparation method and application thereof. BACKGROUND

[0002] At present, the sealing film on the market is mainly aluminum-plastic sealing film containing aluminum foil. However, the production of aluminum has high energy consumption and emission, which will cause great pressure on resources consumption and environment. In order to reduce the use of aluminum foil and relieve the pressure on resources and environment, researchers have explored new sealing film materials, such as paper-plastic sealing film. However, the layers of the paper-plastic sealing film are prone to delamination during the processing process, and bubbles are also prone to occur in the heat-sealed area during heat sealing. In addition, the overall flatness of the embossed and die-cut sealing film cannot meet the requirements of automatic film suction and falling.

[0003] The prior art CN114162449A discloses a dry recovery paper-plastic zipper packaging bag and a preparation method thereof, which comprises the following steps: S1, brushing a single-component polyurethane adhesive on both sides of kraft paper to obtain a first bonding layer and a second bonding layer; S2, printing BOPP film and then compounding the first bonding layer, compounding PET film and the second bonding layer, and then performing curing; S3, brushing a double-component polyurethane adhesive on the side of the PET film away from the second bonding layer to form a third bonding layer, compounding PE film on the third bonding layer, curing, slitting, and forming a composite film; and S4, folding the composite film, placing the zipper of PE material between the PE layers, and heat sealing at 120-150 DEG C and 25-35 N for 0.5-1 s to prepare the dry recovery paper-plastic zipper packaging bag. On the one hand, the present application provides a dry recovery paper-plastic zipper packaging bag rather than a preparation method of sealing film, and does not focus on the overall flatness performance to achieve the requirements of automatic film suction and falling. On the other hand, it mainly improves the delamination problem by using the layers of the dry recovery paper-plastic zipper packaging bag, and does not improve the delamination problem of the paper-plastic film and the problem of bubble generation during heat sealing from the preparation process. SUMMARY

[0004] The present application provides a preparation method of paper-plastic sealing film, which improves the flatness of the paper-plastic sealing film product and is not prone to delamination and bubble generation during heat sealing.

[0005] Another object of the present application is to provide a paper-plastic sealing film.

[0006] Another object of the present application is to provide a paper-plastic sealing film in the field of suction cup sealing.

[0007] In a first aspect, the present application provides a preparation method of a paper-plastic sealing film, comprising the following steps: S1. applying a single-component polyurethane adhesive on one side of a paper base layer to form a first adhesive layer, first compounding a printing layer with the first adhesive layer, winding, and first curing; S2. applying a single-component polyurethane adhesive on the other side of the paper base layer to form a second adhesive layer, second compounding a polyester film layer with the second adhesive layer, winding, and second curing; S3. applying a two-component polyurethane adhesive on the side of the polyester film layer that is not compounded to form a third adhesive layer, third compounding a polyolefin film with the third adhesive layer, winding, and third curing, The ambient temperature for the first, second and third compounding is 25℃±5℃, and the ambient humidity is controlled at 40-55%.

[0008] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the coating amount of the single-component polyurethane adhesive for the first and second compounding is 2.5-3g / m 2 .

[0009] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the winding is reversed after the third compounding.

[0010] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the tension for the reversed winding is 250-350N, the taper is 40-60%, and the speed is 150-250m / min.

[0011] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the temperature for the third curing is 35℃-45℃, and the curing time is ≥72h.

[0012] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the viscosity of the single-component polyurethane adhesive is 5000-6000mPa.s.

[0013] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the basis weight of the paper base layer in S1 is ≥60g / m 2 , and the thickness is ≥50μm.

[0014] According to the preparation method of the paper-plastic sealing film provided by the present application, preferably, the printing layer in S1 is a polyester film printed on the inner side.

[0015] In a second aspect, the present application also provides a paper-plastic sealing film prepared by the preparation method of the paper-plastic sealing film.

[0016] In a third aspect, the present application also provides an application of the paper-plastic sealing film in the field of sealing of vacuum forming cups.

[0017] Advantages: The application provides a paper-plastic sealing film preparation method, which significantly improves the flatness of the paper-plastic sealing film through a multi-pass composite curing preparation process and composite environment parameter control, and the flatness is equivalent to that of an aluminum-plastic sealing film, automatic film suction and film falling processes can be realized, the composite strength of each layer of the paper-plastic sealing film is excellent, the paper-plastic sealing film is not layered, no bubbles appear in the heat-sealed area after heat sealing, the heat-sealing strength after heat sealing is detected, no air leakage is found after 30s under-0.04Mpa negative pressure, the sealing requirement is met, and the paper-plastic sealing film can be widely applied to the packaging and sealing field. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the content of the application more easily and clearly understood, the application is further described in detail below according to specific embodiments of the application and in combination with the drawings.

[0019] Figure 1 It is a single-piece paper-plastic sealing film.

[0020] Figure 2 It is a layer structure schematic diagram in a preparation process of the paper-plastic sealing film, wherein 1 is a polyester film, 2 is a printing layer, 3 is a single-component polyurethane adhesive, 4 is paper, 5 is a single-component polyurethane adhesive, 6 is a polyester film, 7 is a two-component polyurethane adhesive, and 8 is a polyolefin film.

[0021] Figure 3 It is a flatness effect diagram of Example 1.

[0022] Figure 4 It is a flatness effect diagram of Comparative Example 1.

[0023] Figure 5 It is an effect diagram of the paper-plastic sealing film of Examples 1-6 after heat sealing.

[0024] Figure 6 It is an effect diagram of the paper-plastic sealing film of Comparative Example 1 after heat sealing. DETAILED DESCRIPTION

[0025] The following examples are used to illustrate the application, but are not used to limit the scope of the application. If the specific technology or condition is not indicated in the examples, the technology or condition is carried out according to the technology or condition described in the literature in the field, or according to the product instruction. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be purchased through a regular channel.

[0026] In the specific embodiment, the application provides a paper-plastic sealing film preparation method, including the following steps: S1. The single-component polyurethane adhesive is coated on one side of the paper base layer to form a first adhesive layer, the printing layer is first combined with the first adhesive layer, is wound up, and is first cured. S2. A single-component polyurethane adhesive is coated on the other side of the paper base layer to form a second adhesive layer. The polyester film layer is then laminated with the second adhesive layer for the second time, wound up, and cured for the second time. S3. Apply a two-component polyurethane adhesive to the uncoated side of the polyester film layer to form a third adhesive layer. Coat the polyolefin film with the third adhesive layer for the third time, then wind it up and cure it for the third time.

[0027] The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 40~55%.

[0028] It should be noted that: The paper-plastic sealing film preparation method mentioned in this invention, through multi-stage lamination-winding-curing operations combined with temperature and humidity control of the lamination process environment, effectively reduces the water absorption and dampness of the paper during the preparation process, effectively prevents the paper from absorbing moisture and deforming and curling, and solves the problem of delamination of each layer in the paper-plastic sealing film during processing. In addition, the multi-stage lamination-winding-curing process also allows the moisture in the processing process to evaporate completely, and the heat-sealing area is less likely to generate air bubbles during heat sealing. The sealing film after embossing and punching has good flatness, and the overall flatness meets the requirements of automatic film suction and dropping.

[0029] In conventional paper-plastic sealing film preparation methods, adhesives are applied to both sides of a paper base layer, and films of different materials are laminated before a single-pass lamination-curing operation is performed. Alternatively, a single-layer lamination is applied to the paper. Due to differences in the tension of the paper and film on both sides, the shrinkage force on the paper during the lamination process due to adhesive curing, and the uneven shrinkage on both sides of the paper base layer, it is difficult to achieve a balance. Tension deviations between the films on both sides during lamination, and the simultaneous release of tension during uniform curing, exacerbate uneven stretching or shrinkage of the paper, resulting in wavy edges or wrinkles, affecting the overall flatness. In contrast, the multi-pass lamination-curing method of this invention can greatly reduce the flatness problems caused by imbalances on both sides. Furthermore, during the second lamination-curing of the paper base layer, the lamination tension can be adjusted to offset the effects of the first imbalance, ultimately making it easier to balance the shrinkage forces on both sides and significantly reducing unbalanced phenomena such as curling.

[0030] In a specific embodiment, the preparation method of the paper-plastic sealing film mentioned in this invention may further include the following conventional steps: Embossing: The composite film that has undergone three curing processes is embossed using an embossing roller with clear embossing patterns.

[0031] Die-cutting: The embossed composite film is die-cut into single-piece paper-plastic sealing film using a die-cutting mold.

[0032] The first and second curing processes mentioned in this invention can be carried out under conventional curing conditions for paper-plastic sealing film preparation, such as the following curing conditions: curing in a curing chamber at a temperature of 35°C to 40°C for 24 hours.

[0033] In some specific embodiments, to improve the composite strength and ensure that delamination does not occur between the paper and the film, and to reduce the amount of adhesive absorbed by the paper layer to ensure that no bubbles are generated in the heat-sealed area during heat sealing, the present invention further controls the coating amount of the single-component polyurethane adhesive in the first and second composites to be 2.5~3 g / m². 2 For example, the coating weight of the single-component polyurethane adhesive in the first and second laminations can be 2.5 g / m². 2 2.6g / m 2 2.7g / m 2 2.8g / m 2 2.9g / m 2 3.0g / m 2 Equal point values ​​or any range of values.

[0034] In some specific embodiments, in the exemplary method mentioned in this invention, the third lamination is followed by reverse winding. After reverse winding, the outermost layer is a heat-sealable polyolefin film, which can effectively reduce the inward curling force of the printed layer and ensure the flatness of the sealing film after embossing and die-cutting.

[0035] In some specific embodiments, the process parameters for the third composite reverse winding mentioned in this invention include the following: reverse winding tension of 250~350N, taper of 40~60%, and speed of 150~250m / min.

[0036] The winding process parameters have a significant impact on the flatness and bubble control of the prepared paper-plastic sealing film.

[0037] Rewinding tension refers to the tensile force (unit: N) applied to the composite film during the rewinding process. Excessive tension leads to overstretching of the composite film, damaging the fiber structure of the paper substrate and causing irregular deformation (such as wavy edges) when stress is released later. Excessive tension also compresses the adhesive layer, resulting in uneven distribution of the adhesive layer between the films, damaging the interfacial bond between the paper and the plastic film. During later curing, weak areas of the adhesive layer are prone to delamination or insufficient composite strength. Insufficient tension results in loose rewinding, with gaps between the film layers, making the film roll prone to "collapse" due to gravity or external forces. Furthermore, loose film adhesion leads to uneven local stress, forming "bulges" or wrinkles. It also fails to effectively reduce the inward curling force of the printed layer, resulting in poor flatness after embossing and die-cutting.

[0038] For example, the reverse winding tension can be a point value such as 250N, 280N, 300N, 320N, 330N, 350N, or any range of values; for example, the reverse winding taper can be a point value such as 40%, 45%, 50%, 55%, 60%, or any range of values; for example, the reverse winding speed can be a point value such as 150 m / min, 160 m / min, 170 m / min, 180 m / min, 190 m / min, 200 m / min, 210 m / min, 220 m / min, 230 m / min, 240 m / min, 250 m / min, or any range of values.

[0039] In some specific embodiments, in order to better ensure that the moisture between the paper and the composite layer evaporates completely and that no bubbles are generated in the heat-sealed area during heat sealing, the temperature of the third curing is 35℃~45℃ and the curing time is ≥72h.

[0040] In some specific embodiments, in order to achieve better composite strength and better avoid delamination of each layer, the single-component polyurethane adhesive mentioned in this invention is preferably a single-component polyurethane adhesive with a viscosity of 5000~6000 mPa·s.

[0041] In the preparation method of the paper-plastic sealing film of the present invention, the paper base layer can be a conventional paper material that meets the requirements of the paper-plastic sealing film, preferably with a high temperature resistance of 220°C or below. In order to achieve better flatness, in some specific embodiments, the basis weight of the paper base layer mentioned in S1 of the present invention is ≥60g / m³. 2 The thickness is ≥50μm. At this thickness and basis weight, the paper base layer provides better flatness for paper-plastic sealing film products.

[0042] In some specific embodiments, the printing layer mentioned in S1 is an inner-layer printed polyester film.

[0043] In some specific embodiments, the thickness of the polyester film printed on the inner layer mentioned in S1 can be selected as 6~12μm, such as point values ​​or arbitrary range values ​​such as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm.

[0044] The polyester film for inner layer printing can be prepared using the following method: By using environmentally friendly inks that are benzene-free, ketone-free, and low in VOCs on a 6-10 color gravure printing press, reverse printing is performed on the inner layer of a polyester film to form a printed layer, which is then wound up in roll form.

[0045] In a specific embodiment, the present invention also provides a method for preparing a paper-plastic sealing film to obtain a paper-plastic sealing film.

[0046] In some specific embodiments, in order to achieve better heat sealing effect and adapt to the application environment of blister cups, the thickness of the polyolefin film of the heat sealing layer of the paper-plastic sealing film of the present invention can be set to 40-50μm.

[0047] In some specific embodiments, the thickness of the polyester film in the paper-plastic sealing film of the present invention is preferably set to 6~12μm.

[0048] In a specific embodiment, the present invention also provides an application of paper-plastic sealing film in the field of blister cup sealing.

[0049] This invention provides a single-sheet embossed paper-plastic sealing film that is non-layered, bubble-free during heat sealing, and has good flatness. It can be industrialized for use in cup products, and is especially suitable for sealing blister cups.

[0050] Example 1 A method for preparing a paper-plastic sealing film includes the following steps: S1. A one-component polyurethane adhesive (viscosity 6000 mPa·s) is coated onto a paper substrate (basis weight 60 g / m²) using a solventless laminating machine. 2 A first adhesive layer is formed on one side (with a thickness of 50 μm), and the amount of adhesive applied is 2.8 g / m². 2 The printing layer (formed by reverse printing on the inner layer of polyester film using environmentally friendly inks that are free of benzene, ketone, and low in VOCs on a 6-10 color gravure printing machine) is first laminated with the first adhesive layer and then wound up in a roll. First curing: The composite film completed in the first lamination is cured in a curing chamber at 35°C for 24 hours; S2. A second adhesive layer is formed by applying a single-component polyurethane adhesive (viscosity 6000 mPa·s) to the other side of the paper substrate using a solvent-free laminating machine. The adhesive coating amount is 2.8 g / m². 2 The polyester film layer is laminated with the second adhesive layer for a second time and then wound up in a roll. Second curing: The composite film after the second lamination is completed is cured in a curing chamber at 35°C for 24 hours; S3. A two-component polyurethane adhesive is applied to the uncoated side of the polyester film layer using a solventless laminating machine to form a third adhesive layer. The polyolefin film is then laminated with the third adhesive layer for the third time. During winding, reverse winding is selected, with a winding tension of 250N, a taper of 40%, and a speed of 200m / min. Third curing: The composite film after three layers of lamination is cured in a curing chamber at 45°C for 72 hours. The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 50%.

[0051] The preparation method of paper-plastic sealing film may also include the following steps: Embossing: The composite film that has undergone three curing processes is embossed using an embossing roller with clear embossing patterns; Die-cutting: For composite films that have been embossed, die-cutting molds are used to cut them into single sheets of paper-plastic sealing film, such as... Figure 1 As shown. The layer structure in the preparation process of paper-plastic sealing film is as follows. Figure 2 As shown.

[0052] Example 2 A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that: S3. A two-component polyurethane adhesive is applied to the uncoated side of the polyester film layer using a solventless laminating machine to form a third adhesive layer. The polyolefin film is then laminated with the third adhesive layer for the third time. During winding, reverse winding is selected, with a winding tension of 300N, a taper of 50%, and a speed of 220m / min.

[0053] Example 3 A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that: S3. A two-component polyurethane adhesive is applied to the uncoated side of the polyester film layer using a solventless laminating machine to form a third adhesive layer. The polyolefin film is then laminated with the third adhesive layer for the third time. During winding, reverse winding is selected, with a winding tension of 350N, a taper of 55%, and a speed of 230m / min.

[0054] Example 4 A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that: S3. A two-component polyurethane adhesive is applied to the uncoated side of the polyester film layer using a solventless laminating machine to form a third adhesive layer. The polyolefin film is then laminated with the third adhesive layer for the third time. During winding, forward winding is selected, with a winding tension of 250N, a taper of 40%, and a speed of 200m / min.

[0055] Example 5 A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that: Third curing: The composite membrane after three layers of lamination is cured in a curing chamber at 37°C for 24 hours.

[0056] Example 6 A method for preparing a paper-plastic sealing film is basically the same as in Example 1, except that the amount of adhesive applied to form the first and second adhesive layers is 2 g / m². 2 .

[0057] Comparative Example 1 A method for preparing a paper-plastic sealing film, differing from Example 1 in that the printed layers and polyester film layers on both sides of the paper base are prepared by single-pass lamination, including the following steps: S1. A one-component polyurethane adhesive (viscosity 6000 mPa·s) is coated onto a paper substrate (basis weight 60 g / m²) using a solventless laminating machine. 2 A first adhesive layer and a second adhesive layer are formed on both sides of a layer with a thickness of 50 μm, and the amount of adhesive applied is 2.8 g / m². 2 The printing layer (formed by reverse printing on the inner layer of the polyester film using environmentally friendly inks that are free of benzene, ketone, and low VOC on a 6-10 color gravure printing machine) is laminated with the first adhesive layer, and the polyester film layer is laminated with the second adhesive layer, and then wound up in a roll. First curing: The composite membrane is cured at 35°C in a curing chamber for 24 hours. S2. A two-component polyurethane adhesive is applied to the uncoated side of the polyester film layer using a solventless laminating machine to form a third adhesive layer. The polyolefin film is then laminated with the third adhesive layer in a second step. During winding, reverse winding is selected, with a winding tension of 250N, a taper of 40%, and a speed of 200m / min. Second curing: The composite membrane after the second lamination is cured in a curing chamber at 45°C for 72 hours; The ambient temperature of the composite is 25℃±5℃, and the ambient humidity is controlled at 50%.

[0058] The preparation method of paper-plastic sealing film may also include the following steps: Embossing: The composite film after secondary curing is embossed using an embossing roller with clear embossing patterns; Die-cutting: The embossed composite film is die-cut into single-piece paper-plastic sealing film using a die-cutting mold.

[0059] Result detection The paper-plastic sealing film produced using the technical means of this invention exhibits flatness comparable to aluminum-plastic sealing films, superior to existing paper / PE coated paper-plastic sealing films, and enables automated film suction and placement processes. The composite strength of each layer in the paper-plastic sealing film is excellent, with no delamination. After heat sealing, no bubbles appear in the heat-sealed area. The heat-sealing strength is tested, and it remains leak-free for 30 seconds under a negative pressure of -0.04 MPa, meeting the sealing requirements. Simultaneously, sensory, physical, and physicochemical indicators all meet relevant standards. This is a single-sheet embossed paper-plastic sealing film that does not delaminate, produces no bubbles during heat sealing, and exhibits excellent flatness.

[0060] The flatness test method is as follows: Place a single sheet of paper-plastic sealing film flat on the inspection platform and measure it with a measuring tool with an accuracy of 0.5mm. If the edge warping is ≤5mm, it is judged to be flat.

[0061] The method for determining the composite strength is as follows: Cut a paper-plastic composite film with a width of 15mm and a length of 200mm, peel the paper layer and the plastic film layer of the paper-plastic composite film along the interface, and if the paper layer is torn, the composite strength of the paper layer and the plastic layer is deemed to be qualified.

[0062] The method for determining heat seal strength is as follows: According to a certain heat sealing process, a single sheet of paper-plastic sealing film is heat-sealed with a blister cup. The heat-sealed sample is placed under a negative pressure of -0.04 MPa and kept for 30 seconds without leakage. If the heat seal strength is qualified and meets the sealing requirements, it is determined that the heat seal strength is qualified.

[0063] The test results of each embodiment and comparative example are shown in Table 1 below.

[0064] Table 1

[0065] in Figure 3 The image shows the flatness effect of Example 1, indicating good flatness with warpage controlled within 3mm. Other examples also exhibit substantially similar flatness effects.

[0066] Figure 4 The image shows the flatness of Comparative Example 1, which reveals a significant warping phenomenon, with a warping of 7.5mm.

[0067] The paper-plastic sealing films prepared by the methods described in Examples 1-6 produce no air bubbles after heat sealing. Figure 5 As shown. In Comparative Example 1, the paper-plastic sealing film exhibited obvious air bubbles after heat sealing. Figure 6 .

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a paper-plastic sealing film, characterized in that, Includes the following steps: S1. A single-component polyurethane adhesive is applied to one side of the paper base layer to form a first adhesive layer. The printing layer is then laminated with the first adhesive layer for the first time, and the paper is wound up and cured for the first time. S2. A single-component polyurethane adhesive is coated on the other side of the paper base layer to form a second adhesive layer. The polyester film layer is then laminated with the second adhesive layer for the second time, wound up, and cured for the second time. S3. Apply a two-component polyurethane adhesive to the uncoated side of the polyester film layer to form a third adhesive layer. Then, laminate the polyolefin film to the third adhesive layer for the third time, wind it up, and cure it for the third time. The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 40~55%.

2. The method for preparing the paper-plastic sealing film according to claim 1, characterized in that, The coating amount of the single-component polyurethane adhesive used in the first and second composite processes is 2.5-3 g / m². 2 .

3. The method for preparing the paper-plastic sealing film according to claim 1, characterized in that, The third composite is then reverse-wound.

4. The method for preparing the paper-plastic sealing film according to claim 3, characterized in that, The reverse winding tension is 250~350N, the taper is 40~60%, and the speed is 150~250m / min.

5. The method for preparing the paper-plastic sealing film according to claim 1, characterized in that, The third curing temperature is 35℃~45℃, and the curing time is ≥72h.

6. The method for preparing the paper-plastic sealing film according to claim 1, characterized in that, The viscosity of the single-component polyurethane adhesive is 5000-6000 mPa·s.

7. The method for preparing the paper-plastic sealing film according to any one of claims 1 to 6, characterized in that, The basis weight of the paper base layer described in S1 is ≥60g / m³. 2 The thickness is ≥50μm.

8. The method for preparing the paper-plastic sealing film according to any one of claims 1 to 6, characterized in that, The printed layer mentioned in S1 is a polyester film printed on the inner layer.

9. A paper-plastic sealing film prepared by the method of any one of claims 1 to 8.

10. The application of the paper-plastic sealing film of claim 9 in the field of sealing blister cups.

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