Paper-plastic cup package and method for manufacturing the same

Abstract

This invention provides a paper-plastic cup packaging and its preparation method. The packaging contains 150-300 g / m³ of... 2 The cup body and lid are made of paper as the substrate layer. A coated polylactic acid (PLA) barrier layer and a composite heat-sealing layer are sequentially formed on the inner side of the substrate layer. The barrier layer enhances its barrier performance through aluminum / silica / alumina plating. The heat-sealing layer employs a gradient structure of PBS in the center and a PBS / PCL blend at the edges. A 3-5 mm wide linearly increasing PCL mixing zone is incorporated at the edges to optimize thermal stress distribution. The manufacturing method involves a dry lamination process to bond the substrate layer, barrier layer, and heat-sealing layer stepwise, combined with hot pressing and multi-stage curing processes to achieve interlayer bonding. The cup body is formed by rolling and flanging to create a sealing structure that matches the concave ring of the lid. The lid is then heat-sealed integrally with the cup body. This structure utilizes a fully degradable material system, combining excellent oxygen / water barrier properties with reliable heat sealing, making it particularly suitable for the long-shelf-life packaging needs of liquid foods such as yogurt.

Description

Technical Field

[0001] This invention relates to the field of food packaging technology, specifically to a type of packaging, particularly a biodegradable and environmentally friendly paper-plastic cup packaging for yogurt, and also to a method for preparing the paper-plastic cup packaging. Background Technology

[0002] Paper-plastic cups, also known as paper-based composite cups, are food packaging containers made primarily of paper pulp combined with a waterproof coating or plastic film. They are widely used in the beverage, fast food, and cold drink industries. Paper-plastic cups are typically disposable paper cups, achieving their waterproofness through a polymer composite bond. Common materials include polystyrene (PS) cups, polypropylene (PP) cups, and polyethylene (PE) cups. The paper substrate layer provides support, while the polymer is often applied to the inside of the cup using a lamination process. The outer surface of the cup can also be printed with patterns, text, advertisements, etc.

[0003] To improve the leak-proof performance of paper cups, paper-plastic cups with lids were developed. Early lids were mostly made of low-density polyethylene (LDPE) or polypropylene plastic film, which was compatible with the PE coating of the cup body, but was difficult to recycle or degrade, thus burdening the environment.

[0004] Furthermore, it's worth noting that existing paper-plastic cup packaging requires superior barrier properties when used for products such as yogurt, beverages, and alcoholic drinks to extend the shelf life of liquid foods. However, the barrier performance requirements for liquid foods are quite complex. Yogurt needs to block oxygen and light; alcoholic drinks require high moisture barrier properties; and acidic beverages require resistance to chemical corrosion. Currently, mainstream PE / PP coatings only provide basic waterproofing and cannot meet the requirements for long shelf life. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a paper-plastic cup packaging that has good multi-dimensional barrier properties and excellent molding and processing characteristics, and is also biodegradable.

[0006] To achieve the above objectives, the present invention provides a paper-plastic cup packaging, comprising a cup body and a lid film. Both the cup body and the lid film are made of paper as the substrate layer. A barrier layer and a heat-sealing layer are sequentially disposed on the inner side of the substrate layer. The barrier layer is made of coated polylactic acid and covers the inner surface of the substrate layer. The center of the heat-sealing layer is made of polybutylene succinate (PBS), and the edges of the heat-sealing layer are a blend of polybutylene succinate and polycaprolactone (PCL). "Inner side" refers to the side facing the packaged item.

[0007] Furthermore, the basis weight of the cup body paper is between 150-300 g / m². 2 The weight of the cover paper is 40-90 g / m². 2 .

[0008] Furthermore, the melt index of the polybutylene succinate in the center of the heat-sealing layer is 18-22 g / 10 min, and the edge layer is formed by extruding a mixture of polybutylene succinate and polycaprolactone at a mass ratio of 1:0.2-0.3.

[0009] Furthermore, a gradient mixing zone with a width of 3-5 mm is provided between the edge and center of the heat-sealing layer, and the content of polycaprolactone increases linearly from the center to the edge of the heat-sealing layer.

[0010] As an explanation, the linear increase in polycaprolactone content in the gradient mixing zone can be achieved using co-extrusion molding, multi-layer coating, or dynamic mixing technology. For example, a segmented temperature control process using a twin-screw extruder can be employed, with the PBS zone at 180°C and the PCL zone at 120°C, and the mixing ratio can be adjusted separately using mass flow controller parameters.

[0011] Furthermore, the coated polylactic acid is a polylactic acid film with at least one of aluminum, silicon oxide, and aluminum oxide deposited on its surface, and the coating thickness is 50-200 nm. The polylactic acid surface coating can be performed using a vacuum evaporation method.

[0012] Furthermore, it also includes a lid, the inner side of which is provided with a concave ring, and the opening of the cup body is provided with a flange adapted to the concave ring, and the blend of polybutylene succinate and polycaprolactone covers the flange and / or the concave ring.

[0013] Secondly, the present invention provides a method for preparing a yogurt paper-plastic cup package having any one or more of the above-mentioned technical features, comprising the following steps: S1, the paper of the substrate layer is laid flat on the dry laminator, glue is applied to its surface and then bonded to the barrier layer, and the first curing is performed. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center and edge part to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The edge part of the heat-sealing layer extends to the outside of the substrate layer to form a connecting part. S3, heat-press the intermediate body of the paper-plastic cup packaging to connect the center and edge of the heat-sealing layer as a whole; S4, the intermediate material for paper-plastic cup packaging undergoes a second curing process; S5, surround the cup body and heat-seal the seam of the cup body together to form a whole through the connecting part, transfer the cup body to the paper cup flanging machine for flanging, and heat-seal the lid film to the cup mouth of the cup body.

[0014] Furthermore, it also includes S6, which involves cutting and stamping the substrate layer-barrier layer according to the shape of the cover to obtain a cover with a concave ring on the inner side. After fastening the cover to the cup, heat-sealing is performed along the outer periphery of the cover to make the edge of the heat-sealing layer of the cup interfere with the concave ring.

[0015] As an explanation, the cup shape in S2 includes, but is not limited to, a fan-shaped body and a circular base. The cup body can have at least partially overlapped and connected along its two radii, and then the circular base can be connected to the opening of the body. The lid can be manufactured using a similar method.

[0016] Furthermore, in step S1, a 3-5 g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.3-0.5 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing, which is carried out at 45°C for 24 hours. And / or, in S2, a gradient mixing zone with a width of 3-5 mm is further provided between the center and the edge of the heat-sealing layer; And / or, in S3, the hot pressing process includes heating the cup body to 185-195°C, initially pressurizing 5MPa, finally holding the pressure at 8-10MPa, and holding the pressure for 8-12s. And / or, in S4, the intermediate paper-plastic cup packaging is transferred to a curing chamber for a second curing, the second curing conditions being 50°C for 48 hours; And / or, in S5, mechanical rolling is used for flanging, the roller temperature is set to 135-145℃, the forming pressure is 0.8-1.2MPa, the rolling linear speed is 4-6m / min, the roller gap is 1.2-1.5mm, and the number of rolling cycles for a single cup body is not less than 3. And / or, in S6, a hot air blower is used to heat the outer periphery of the lid, so that the temperature of the lid reaches 155-165℃, and heat-seales it with the cup body.

[0017] Thirdly, the present invention also provides a paper-plastic packaging cup prepared based on the above-mentioned technical content, which is used for packaging liquid foods such as beverages and wines.

[0018] The advantages and beneficial effects of this invention are as follows: 1. The paper-plastic cup packaging substrate layer provided by this invention uses paper, the barrier layer uses coated polylactic acid (PLA), and the heat-sealing layer comprises polybutylene succinate (PCL) and polycaprolactone (PVC) as its core materials, all of which are biodegradable or compostable. Compared with traditional PE / PP coatings, the degradation cycle is shortened. By blending PCL and PET, the degradation efficiency at the edges is improved while ensuring heat-sealing performance. The coated PLA layer provides oxygen and water barrier properties, meeting the barrier requirements of different liquid foods.

[0019] 2. The center of the heat-sealing layer uses high-melting-point PET to ensure heat-sealing strength, while the edge uses a PCL / PBS blend to improve low-temperature heat-sealing adaptability. The gradient mixing zone can also alleviate thermal stress through the linear increase of polycaprolactone content. The cover-cup body interference seal, the concave ring and the flange structure work together with the edge of the heat-sealing layer to achieve a dual seal of mechanical and thermal fusion, providing protection for the joint between the cover film and the cup body. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the disassembly structure of the paper-plastic cup packaging of the present invention; Figure 2 This is a schematic diagram of the structure of the paper-plastic cup packaging body after cutting according to the present invention; Figure 3 This is a flowchart of the paper-plastic cup packaging preparation method of the present invention; In the diagram: 1-Cup body, 2-Cover film, 3-Cover body, 4-Substrate layer, 5-Barrier layer, 6-Heat-sealing layer, 7-Center of heat-sealing layer, 8-Edge of heat-sealing layer, 9-Gradient mixing zone. Detailed Implementation

[0021] This invention provides a paper-plastic cup packaging, comprising a cup body 1, a lid film 2 heat-sealed to the cup body, and optionally a lid body 3. The cup body 1, lid film 2, and lid body 3 each include a substrate layer 4, a barrier layer 5, and a heat-sealing layer 6 stacked sequentially. The heat-sealing layer 6 is further divided into a central portion 7 and an edge portion 8, and optionally, a gradient mixing zone 9 is provided in the central and edge portions of the heat-sealing layer. This invention employs a three-layer composite structure of a substrate layer, a coated PLA barrier layer, and a heat-sealing layer, balancing mechanical strength, barrier performance, and heat-sealing reliability. The cup body flange and the lid recess are mechanically rolled to form a fitted flange structure, creating an interference fit with the lid recess. Combined with the PCL blend at the edge of the heat-sealing layer, this achieves dual protection of mechanical fitting and heat-sealing. It is particularly suitable for liquid foods requiring long shelf life and high barrier requirements.

[0022] This invention utilizes a paper substrate layer to provide basic support and biodegradability. The barrier layer is formed on polylactic acid through vacuum deposition. The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] Example 1 A paper-plastic cup packaging, comprising a cup body and a lid film, wherein the cup body is made of 200g / m³ material. 2 The paper is used as the base layer, and the cover film is made of 50g / m². 2The paper is the substrate layer. Inside the substrate layer, there is a 100nm thick aluminum-plated PLA barrier layer and a heat-sealing layer. The center of the heat-sealing layer is PBS with a melt index of 18g / 10min. The heat-sealing layer has a 7mm wide edge. The edge of the heat-sealing layer is a film layer co-extruded from PBS and PCL at a mass ratio of 1:0.25.

[0024] The preparation method of this paper-plastic cup packaging structure is as follows: S1, the paper for the substrate layer is laid flat on the dry laminator, and then a 3g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.3 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center and edge part to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The edge part of the heat-sealing layer extends to the outside of the substrate layer to form a connecting part. S3, transfer the intermediate paper-plastic cup packaging to the hot press at 185°C, starting from 5MPa, slowly increase the pressure to 8MPa, hold the pressure for 10s, so that the center and edge of the heat seal layer are integrally connected. S4, the intermediate material for paper-plastic cup packaging undergoes a second curing process; S5. Enclose the cup body and heat-seal the seam of the cup body together through the connecting part to form a whole. Transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging. The roller temperature is set to 140℃, the forming pressure is 1MPa, the rolling line speed is 4m / min, the roller gap is 1.2mm, and after rolling each cup body 3 times, the lid film is covered with the cup mouth and then heat-sealed.

[0025] Example 2 A paper-plastic cup packaging includes a cup body, a lid film, and a lid with a concave ring on the inner side. The cup body and lid are made of 150g / m³ material. 2 The paper is used as the base layer, and the cover film is made of 40g / m². 2 The paper serves as the substrate layer, with a 100nm thick silicon oxide-coated PLA barrier layer and a heat-sealing layer sequentially disposed on the inner side of the substrate layer. The center of the heat-sealing layer is PBS with a melt index of 22g / 10min, and the heat-sealing layer has a 6mm wide edge, which is formed by extruding a blend of PBS and PCL at a ratio of 1:0.2. A 5mm wide gradient mixing zone is set between the edge and the center of the heat-sealing layer, and the PCL content in the gradient mixing zone increases linearly from the center to the edge of the heat-sealing layer to 20%.

[0026] The preparation method of this paper-plastic cup packaging structure is as follows: S1, the paper for the substrate layer is laid flat on the dry laminator, and then a 5g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.5 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center, heat-sealing layer edge, and gradient mixing zone to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The heat-sealing layer edge extends to the outside of the substrate layer to form a connecting part. S3, transfer the intermediate paper-plastic cup packaging to the hot press at 195°C, start hot pressing from 5MPa, slowly increase the pressure to 10MPa, hold the pressure for 12s, so that the center and edge of the heat seal layer are integrally connected. S4, undergo a second curing process at 50℃ for 48 hours; S5. The cup body is surrounded and the seam of the cup body is heat-sealed together through the connecting part. The cup body is then transferred to the paper cup flanging machine for mechanical rolling and flanging. The roller temperature is set to 135℃, the forming pressure is 1.2MPa, the rolling line speed is 6m / min, the roller gap is 1.5mm, and after rolling each cup body 4 times, the lid film is covered with the cup mouth and then heat-sealed.

[0027] S6, the concave ring of the cover and the flange of the cup body are interference fit, and the outer circumference is heat-sealed at 165℃.

[0028] Example 3 A paper-plastic cup packaging includes a cup body, a lid film, and a lid with a concave ring on the inner side. The cup body and lid are made of 300g / m³ material. 2 The paper is used as the base layer, and the cover film is made of 90g / m². 2 The paper serves as the substrate layer, with a 200nm thick aluminum / alumina double-coated PLA barrier layer and a heat-sealing layer sequentially disposed on the inner side of the substrate layer. The center of the heat-sealing layer is PBS with a melt index of 21g / 10min, and the heat-sealing layer has a 5mm wide edge, which is formed by extruding PBS and PCL in a 1:0.3 ratio. A 5mm wide gradient mixing zone is set between the edge and the center of the heat-sealing layer, and the PCL content in the gradient mixing zone increases linearly from the center to the edge of the heat-sealing layer to 30%.

[0029] The preparation method of this paper-plastic cup packaging structure is as follows: S1, the paper for the substrate layer is laid flat on a dry laminator, and then a 4.5 g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.3 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center, heat-sealing layer edge, and gradient mixing zone to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The heat-sealing layer edge extends to the outside of the substrate layer to form a connecting part. S3, transfer the intermediate paper-plastic cup packaging to the hot press at 190°C, start hot pressing from 5MPa, slowly increase the pressure to 8MPa, hold the pressure for 10s, so that the center and edge of the heat seal layer are integrally connected. S4, undergo a second curing process at 50℃ for 48 hours; S5. The cup body is surrounded and the seam of the cup body is pre-sealed by laser through the connecting part and then reinforced by secondary hot pressing. The cup body is transferred to the paper cup flanging machine for mechanical rolling and flanging. The roller temperature is set to 145℃, the forming pressure is 0.8MPa, the rolling line speed is 5m / min, the roller gap is 1.5mm, and after rolling each cup body 5 times, the lid film is covered with the cup mouth and then heat-sealed.

[0030] S6, the concave ring of the cover and the flange of the cup body are interference fit, and the outer circumference is heat-sealed at 160℃.

[0031] Example 4 A paper-plastic cup packaging includes a cup body, a lid film, and a lid with a concave ring on the inner side. The cup body and lid are made of 225g / m³ material. 2 The paper is used as the base layer, and the cover film is made of 60g / m². 2 The paper serves as the substrate layer, with a PLA barrier layer and a heat-sealing layer sequentially arranged inside the substrate layer, each coated with 150nm alumina. The center of the heat-sealing layer contains PBS with a melt index of 19g / 10min, and the heat-sealing layer has a 10mm wide edge, formed by extruding a blend of PBS and PCL at a ratio of 1:0.25. A 5mm wide gradient mixing zone is set between the edge and the center of the heat-sealing layer, with the PCL content in the gradient mixing zone increasing linearly from the center to the edge to 25%.

[0032] The preparation method of this paper-plastic cup packaging structure is as follows: S1, the paper for the substrate layer is laid flat on the dry laminator, and then a 4g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.4 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center, heat-sealing layer edge, and gradient mixing zone to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The heat-sealing layer edge extends to the outside of the substrate layer to form a connecting part. S3, transfer the intermediate paper-plastic cup packaging to the hot press at 195°C, start hot pressing from 5MPa, slowly increase the pressure to 10MPa, hold the pressure for 8s, so that the center and edge of the heat seal layer are integrally connected. S4, undergo a second curing process at 50℃ for 48 hours; S5. Enclose the cup body and connect the seams of the cup body together through the connecting part. Then transfer the cup body to the paper cup flanging machine for mechanical rolling and flanging. The roller temperature is set to 135℃, the forming pressure is 1MPa, the rolling line speed is 5m / min, the roller gap is 1.3mm, and after rolling each cup body 3 times, the lid film is closed to the cup mouth and then heat-sealed.

[0033] S6, the concave ring of the cover and the flange of the cup body are interference fit, and the outer circumference is heat-sealed at 155℃.

[0034] Comparative Example The only difference from Example 1 is that the heat-sealing layer is pure PBS that is completely bonded to the barrier layer, without any partitioning.

[0035] Performance tests were conducted on the above embodiments and comparative examples, and the test results are shown in the table below. Specifically, heat seal strength was tested according to ASTM F88, with the heat-sealed area cut into 15mm wide specimens and stretched at 50mm / min until fracture, recording the maximum load. Degradability was tested according to ISO 14855 in a 58℃ composting environment for 90 days, and the mass loss rate was calculated. Flexural modulus was tested according to ASTM D790, with specimens measuring 80×10×4mm, and the slope of the elastic deformation zone was calculated under a span of 64mm and a loading rate of 2mm / min. Barrier performance was tested according to ASTM D3985 at 23℃ and 0%RH for oxygen permeability, and according to ASTM E96 at 38℃ and 90%RH for water vapor permeability. Seal failure probability was tested according to GB / T 15171, by applying a -80kPa negative pressure to the sealed sample and maintaining it for 30 minutes, and the proportion of leaking samples was statistically analyzed. As shown in the table above, using paper of different weights as the substrate layer in the examples helps to change the rigidity of the cup. The higher the edge content of PCL in the heat-sealing layer, the faster the degradation and the shorter the degradation cycle compared to pure PBS. Examples 2-4 show that by linearly increasing the PCL content, edge cracks are reduced and water and oxygen barrier properties are improved. Using PCL can also effectively improve the sealing effect of paper-plastic cups.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A paper-plastic cup packaging, comprising a cup body and a lid film, characterized in that, Both the cup body and the lid film are made of paper as the base material layer. A barrier layer and a heat-sealing layer are sequentially provided on the inner side of the base material layer. The barrier layer is made of coated polylactic acid and covers the inner side of the base material layer. The center of the heat-sealing layer is made of polybutylene succinate, and the edge of the heat-sealing layer is a blend of polybutylene succinate and polycaprolactone. The melt index of polybutylene succinate in the center of the heat-sealing layer is 18-22 g / 10 min, and the edge layer is formed by extruding a mixture of polybutylene succinate and polycaprolactone at a mass ratio of 1:0.2-0.

3. A gradient mixing zone with a width of 3-5 mm is provided between the edge and the center of the heat-sealing layer, and the content of polycaprolactone increases linearly from the center to the edge of the heat-sealing layer.

2. The paper-plastic cup packaging according to claim 1, characterized in that, The paper used for the cup body has a basis weight of 150-300 g / m². 2 The weight of the cover paper is 40-90 g / m². 2 .

3. The paper-plastic cup packaging according to claim 1, characterized in that, The coated polylactic acid is a polylactic acid film with at least one of aluminum, silicon oxide, and aluminum oxide deposited on its surface, and the coating thickness is 50-200 nm.

4. The paper-plastic cup packaging according to claim 3, characterized in that, It also includes a lid, the inner side of which is provided with a concave ring, and the opening of the cup body is provided with a flange adapted to the concave ring, and the blend of polybutylene succinate and polycaprolactone covers the flange and / or the concave ring.

5. A method for preparing a paper-plastic cup packaging according to any one of claims 1-4, characterized in that, Includes the following steps: S1, the paper of the substrate layer is laid flat on the dry laminator, glue is applied to its surface and then bonded to the barrier layer, and the first curing is performed. S2, cut the substrate layer and barrier layer according to the shape of the cup, apply glue to the side of the barrier layer away from the substrate layer, and dry-composite the pre-cut heat-sealing layer center and edge part to the surface of the barrier layer to form a paper-plastic cup packaging intermediate. The edge part of the heat-sealing layer extends to the outside of the substrate layer to form a connecting part. S3, heat-press the intermediate body of the paper-plastic cup packaging to connect the center and edge of the heat-sealing layer as a whole; S4, the intermediate material for paper-plastic cup packaging undergoes a second curing process; S5, surround the cup body and heat-seal the seam of the cup body together to form a whole through the connecting part, transfer the cup body to the paper cup flanging machine for flanging, and heat-seal the lid film to the cup mouth of the cup body.

6. The preparation method according to claim 5, characterized in that, It also includes S6, which involves cutting and stamping the substrate layer-barrier layer according to the shape of the cover to obtain a cover with a concave ring on the inner side. After fastening the cover to the cup, heat-sealing is performed along the outer periphery of the cover to make the edge of the heat-sealing layer of the cup interfere with the concave ring.

7. The preparation method according to claim 6, characterized in that, In step S1, a 3-5 g / m² coating is applied to the surface of the substrate layer using gravure coating. 2 Polyurethane adhesive is used to bond the substrate layer and barrier layer together on a laminating machine under pressure of 0.3-0.5 MPa. The substrate layer-barrier layer is then placed in a curing chamber for the first curing, which is carried out at 45°C for 24 hours. And / or, in S2, a gradient mixing zone with a width of 3-5 mm is further provided between the center and the edge of the heat-sealing layer; And / or, in S3, the hot pressing process includes heating the cup body to 185-195°C, initially pressurizing 5MPa, finally holding the pressure at 8-10MPa, and holding the pressure for 8-12s. And / or, in S4, the intermediate paper-plastic cup packaging is transferred to a curing chamber for a second curing, the second curing conditions being 50°C for 48 hours; And / or, in S5, mechanical rolling is used for flanging, the roller temperature is set to 135-145℃, the forming pressure is 0.8-1.2MPa, the rolling linear speed is 4-6m / min, the roller gap is 1.2-1.5mm, and the number of rolling cycles for a single cup body is not less than 3. And / or, in S6, a hot air blower is used to heat the outer periphery of the lid, so that the temperature of the lid reaches 155-165℃, and heat-seales it with the cup body.

8. The application of the paper-plastic cup packaging as described in any one of claims 1-4 in liquid food.

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