Paper-plastic sealing film, preparation method and application thereof

Abstract

The application provides a paper-plastic sealing film and 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, a single-component polyurethane adhesive is coated on one side of a paper base layer to form a first adhesive layer, a printing layer is first combined with the first adhesive layer, winding is performed, and first aging is performed; S2, a single-component polyurethane adhesive is coated on the other side of the paper base layer to form a second adhesive layer, a polyester film layer is secondly combined with the second adhesive layer, winding is performed, and second aging is performed; and S3, a two-component polyurethane adhesive is coated on the side of the polyester film layer which is not combined to form a third adhesive layer, a polyolefin film is thirdly combined with the third adhesive layer, winding is performed, and third aging is performed.The paper-plastic sealing film prepared by the method has the advantages of improved flatness, excellent composite strength, no delamination, and no bubbles after heat sealing.

Description

Technical Field

[0001] This invention relates to the field of sealing film technology, and in particular to a paper-plastic sealing film, its preparation method, and its application. Background Technology

[0002] Currently, the sealing films on the market are mainly aluminum-plastic sealing films containing aluminum foil. However, aluminum production consumes a great deal of energy and emits high levels of pollutants, putting significant pressure on resources and the environment. To reduce the use of aluminum foil and alleviate resource and environmental pressures, researchers are exploring new sealing film materials, such as paper-plastic sealing films. However, current paper-plastic sealing films are prone to delamination during processing, and air bubbles are easily generated in the heat-sealed area during heat sealing. Furthermore, the overall flatness of the embossed and die-cut sealing film cannot meet the requirements of automatic film suction and dropping.

[0003] Existing technology CN114162449A discloses a dry-laminated paper-plastic zipper packaging bag and its preparation method, including the following steps: S1, applying a single-component polyurethane adhesive to both sides of kraft paper to obtain a first adhesive layer and a second adhesive layer; S2, printing BOPP film and laminating it with the first adhesive layer, laminating a PET film with the second adhesive layer, and then curing; S3, applying a two-component polyurethane adhesive to the side of the PET film away from the second adhesive layer to form a third adhesive layer, laminating a PE film onto the third adhesive layer, curing, and cutting to form a composite film; S4, folding the composite film, placing a PE zipper between the PE layers, and heat-sealing for 0.5-1s at 120-150℃ and 25-35N to produce a dry-laminated paper-plastic zipper packaging bag. However, this existing technology provides a dry-laminated paper-plastic zipper packaging bag rather than a sealing film, and it does not focus on the overall flatness performance to achieve the automatic film suction and dropping requirements. On the other hand, it mainly improves the bonding and delamination problem by using different layers of materials in the dry-coated paper-plastic zipper packaging bag, but does not improve the delamination problem of the paper-plastic film or the problem of air bubbles generated during heat sealing from the manufacturing process. Summary of the Invention

[0004] This invention addresses the shortcomings of current paper-plastic sealing film preparation methods, which generally suffer from issues such as product flatness failing to meet the requirements of automatic film suction and placement, easy layer delamination during processing, and the formation of air bubbles during heat sealing. It provides a paper-plastic sealing film preparation method that improves the flatness of the product through a specific preparation process, making it less prone to delamination and preventing air bubble formation during heat sealing.

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

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

[0007] In a first aspect, the present invention provides a method for preparing a paper-plastic sealing film, comprising the following steps:

[0008] 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, wound up, and cured for the first time.

[0009] S2. A single-component polyurethane adhesive is applied to 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.

[0010] 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.

[0011] The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 40~55%.

[0012] According to the preparation method of the paper-plastic sealing film provided by the present invention, preferably, the coating amount of the single-component polyurethane adhesive in the first and second laminations is 2.5~3 g / m². 2 .

[0013] According to the paper-plastic sealing film preparation method provided by the present invention, preferably, the third lamination is reverse-winding.

[0014] According to the paper-plastic sealing film preparation method provided by the present invention, preferably, the reverse winding tension is 250~350N, the taper is 40~60%, and the speed is 150~250m / min.

[0015] According to the preparation method of paper-plastic sealing film provided by the present invention, preferably, the temperature of the third curing is 35℃~45℃ and the curing time is ≥72h.

[0016] According to the preparation method of the paper-plastic sealing film provided by the present invention, preferably, the viscosity of the single-component polyurethane adhesive is 5000~6000 mPa·s.

[0017] According to the preparation method of the paper-plastic sealing film provided by the present invention, preferably, the basis weight of the paper base layer in S1 is ≥60g / m³. 2 The thickness is ≥50μm.

[0018] According to the paper-plastic sealing film preparation method provided by the present invention, preferably, the printing layer in S1 is an inner-layer back-printed polyester film.

[0019] Secondly, the present invention also provides a method for preparing a paper-plastic sealing film to obtain a paper-plastic sealing film.

[0020] Thirdly, the present invention also provides an application of paper-plastic sealing film in the field of blister cup sealing.

[0021] Beneficial effects:

[0022] This invention provides a method for preparing paper-plastic sealing film. Through a multi-stage composite curing process and control of composite environmental parameters, the flatness of the paper-plastic sealing film is significantly improved, reaching a flatness comparable to that of aluminum-plastic sealing film. It enables an automatic film suction and placement process, and the composite strength of each layer in the paper-plastic sealing film is excellent, without delamination. No air bubbles appear in the heat-sealed area after heat sealing. The heat-sealing strength after heat sealing is tested, and it remains leak-free for 30 seconds under a negative pressure of -0.04 MPa, meeting the sealing requirements. This method can be widely used in the packaging sealing field. Attached Figure Description

[0023] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Figure 1 It is a single-sheet paper-plastic sealing film.

[0025] Figure 2 This is a schematic diagram of the layer structure in the preparation process of paper-plastic sealing film, where 1-polyester film, 2-printed layer, 3-one-component polyurethane adhesive, 4-paper, 5-one-component polyurethane adhesive, 6-polyester film, 7-two-component polyurethane adhesive, and 8-polyolefin film.

[0026] Figure 3 This is a diagram showing the flatness effect of Example 1.

[0027] Figure 4 This is a diagram showing the flatness effect of Comparative Example 1.

[0028] Figure 5 The images show the heat-sealed effects of the paper-plastic sealing film in Examples 1-6.

[0029] Figure 6 This is a diagram showing the heat-sealed effect of the paper-plastic sealing film in Comparative Example 1. Detailed Implementation

[0030] The following examples are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the examples, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased from legitimate channels.

[0031] In a specific embodiment, the present invention provides a method for preparing a paper-plastic sealing film, comprising the following steps:

[0032] 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, wound up, and cured for the first time.

[0033] S2. A single-component polyurethane adhesive is applied to 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.

[0034] 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.

[0035] The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 40~55%.

[0036] It should be noted that:

[0037] 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.

[0038] 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.

[0039] In a specific embodiment, the preparation method of the paper-plastic sealing film mentioned in this invention may further include the following conventional steps:

[0040] Embossing: The composite film that has undergone three curing processes is embossed using an embossing roller with clear embossing patterns.

[0041] Die-cutting: The embossed composite film is die-cut into single-piece paper-plastic sealing film using a die-cutting mold.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] The winding process parameters have a significant impact on the flatness and bubble control of the prepared paper-plastic sealing film.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In some specific embodiments, the printing layer mentioned in S1 is an inner-layer printed polyester film.

[0053] 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.

[0054] The polyester film for inner layer printing can be prepared using the following method:

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] In a specific embodiment, the present invention also provides an application of paper-plastic sealing film in the field of blister cup sealing.

[0060] 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.

[0061] Example 1

[0062] A method for preparing a paper-plastic sealing film includes the following steps:

[0063] 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.

[0064] First curing: The composite film completed in the first lamination is cured in a curing chamber at 35°C for 24 hours;

[0065] 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.

[0066] Second curing: The composite film after the second lamination is completed is cured in a curing chamber at 35°C for 24 hours;

[0067] 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.

[0068] Third curing: The composite film after three layers of lamination is cured in a curing chamber at 45°C for 72 hours.

[0069] The ambient temperature for the first, second, and third composite processes is 25℃±5℃, and the ambient humidity is controlled at 50%.

[0070] The preparation method of paper-plastic sealing film may also include the following steps:

[0071] Embossing: The composite film that has undergone three curing processes is embossed using an embossing roller with clear embossing patterns;

[0072] 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.

[0073] Example 2

[0074] A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that:

[0075] 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.

[0076] Example 3

[0077] A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that:

[0078] 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.

[0079] Example 4

[0080] A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that:

[0081] 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.

[0082] Example 5

[0083] A method for preparing a paper-plastic sealing film is basically the same as that in Example 1, except that:

[0084] Third curing: The composite membrane after three layers of lamination is cured in a curing chamber at 37°C for 24 hours.

[0085] Example 6

[0086] 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 .

[0087] Comparative Example 1

[0088] 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:

[0089] 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.

[0090] First curing: The composite membrane is cured at 35°C in a curing chamber for 24 hours.

[0091] 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.

[0092] Second curing: The composite membrane after the second lamination is cured in a curing chamber at 45°C for 72 hours;

[0093] The ambient temperature of the composite is 25℃±5℃, and the ambient humidity is controlled at 50%.

[0094] The preparation method of paper-plastic sealing film may also include the following steps:

[0095] Embossing: The composite film after secondary curing is embossed using an embossing roller with clear embossing patterns;

[0096] Die-cutting: The embossed composite film is die-cut into single-piece paper-plastic sealing film using a die-cutting mold.

[0097] Result detection

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] The test results of each embodiment and comparative example are shown in Table 1 below.

[0103] Table 1

[0104]

[0105] 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.

[0106] Figure 4 The image shows the flatness of Comparative Example 1, which reveals a significant warping phenomenon, with a warping of 7.5mm.

[0107] The paper-plastic sealing films prepared by the methods described in Examples 1-6 produce no air bubbles after heat sealing. Figure 5As shown. In Comparative Example 1, the paper-plastic sealing film exhibited obvious air bubbles after heat sealing. Figure 6 .

[0108] 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 was 25℃±5℃, and the ambient humidity was controlled at 40~55%. The third composite winding is followed by reverse winding, with a reverse winding tension of 250~350N, a taper of 40~60%, and a speed of 150~250m / min.

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 curing temperature is 35℃~45℃, and the curing time is ≥72h.

4. 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.

5. The method for preparing the paper-plastic sealing film according to any one of claims 1 to 4, characterized in that, The basis weight of the paper base layer described in S1 is ≥60g / m³. 2 The thickness is ≥50μm.

6. The method for preparing the paper-plastic sealing film according to any one of claims 1 to 4, characterized in that, The printed layer mentioned in S1 is a polyester film printed on the inner layer.

7. A paper-plastic sealing film prepared by the method of any one of claims 1 to 6.

8. The application of the paper-plastic sealing film of claim 7 in the field of blister cup sealing.

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