TWI900995B - Film-coated fiber substrate, and fabricating method thereof - Google Patents

Abstract

A polymethylpentene film, a film-coated fiber substrate, and a fabricating method thereof are provided. The polymethylpentene film in order includes a functional surface layer, a base layer and an adhesive layer. The functional surface layer is made of a functional material, the base layer is made of a polymeric material, and the adhesive layer is made of a low-temperature heat-sealable material. The polymethylpentene film is bonded to a fiber base layer through the adhesive layer to form the film-coated fiber substrate, and the film-coated fiber substrate can be used to prepare a film-coated fiber container. Therefore, the film-coated fiber container with heat resistance, resistance to hot oil penetration, food non-stickiness, scratch resistance and high food hygiene safety can be obtained.

Description

Film-coated paper-plastic substrate and preparation method thereof

The present invention relates to a film, a film-coated substrate, and a preparation method thereof, in particular to a polymethylpentene film, a film-coated paper-plastic substrate, and a preparation method thereof.

In today's bustling world, with its developed commerce and industry, fast food and takeout are incredibly popular. To ensure that food is served quickly, conveniently, and cleanly, restaurants often use disposable tableware for food and drinks. With environmental protection gaining increasing attention worldwide, global initiatives to reduce carbon emissions, promote a circular economy, utilize biomass renewable energy, utilize biodegradable and recyclable materials, and reduce the use of plastic products have become common goals for many countries. As a result, most restaurants are using laminated paper and plastic containers (such as paper boxes, cups, bowls, and plates) for food and drinks. Consequently, laminated paper and plastic containers are gradually replacing plastic containers.

Laminated paper-plastic containers combine the environmental friendliness of paper with the waterproof and oil-resistant packaging properties of plastic. Plastic material is applied to the surface of the paper-plastic container in the form of a film. The plastic material accounts for approximately 10% of the total container weight, effectively reducing plastic usage and potentially replacing some plastic containers. The film material influences the subsequent properties of the laminated paper-plastic container. Common film materials include polyethylene, polypropylene, polylactic acid, and polyethylene terephthalate.

The film used in commercially available laminated paper-plastic containers is mostly made from a blend of polyethylene and polypropylene, laminated onto a paper layer. The resulting laminated paper-plastic substrate for paper cups and boxes has a minimum heat resistance of approximately 70°C. Polylactic acid is biodegradable, but its durability and heat resistance are insufficient. Polyethylene terephthalate, on the other hand, is resistant to acids, alkalis, oils, water, and has excellent gas barrier properties, but its heat resistance is limited to approximately 60°C to 85°C. While coated paper-plastic containers made from these film materials are waterproof, oil-proof, and heat-resistant, they often exceed their heat-resistant temperature when used to store hot foods, such as freshly boiled soup or porridge. This can lead to the release of plasticizers and degradation products into the food. Long-term consumption of hot foods packaged in this manner can easily lead to the accumulation of harmful substances in the body, seriously affecting health. Therefore, it is crucial to address the shortcomings of existing technologies.

One object of the present invention is to provide a polymethylpentene film, a coated paper-plastic substrate and a preparation method thereof that have good heat resistance and hot oil permeation resistance and are highly food hygienic and safe, so as to prepare a coated paper-plastic container that can be heated in a microwave oven or oven using an environmentally friendly material or recycled material that can replace plastic or reduce plastic. The coated paper-plastic container has excellent heat resistance, hot oil permeation resistance, food non-sticking property, and scratch resistance. Safety, food hygiene The improved safety, heat deformation resistance, and freeze resistance of current coated paper-plastic containers enhance their resistance to high-temperature oil penetration and meet the functional requirements of food packaging. Consequently, these coated paper-plastic containers can be used for storing, preserving, and heating food or liquids. They also address the issue of burns caused by hot plastic packaging containers, making them a viable alternative to existing plastic containers used in ready-to-eat foods and a potential solution to reducing the use of disposable plastic containers. Furthermore, the material used in these coated paper-plastic containers can be burned in incinerators to recover heat without compromising the incinerator's functionality.

One aspect of the present invention provides a polymethylpentene film comprising a functional surface layer, a base layer, and an adhesive layer. The functional surface layer is formed from a functional material, wherein the functional material is polymethylpentene or a blend of polymethylpentene and a polyolefin resin, wherein a monomer of the polyolefin resin is a C2-C4 olefin molecule, and the content of polymethylpentene in the blend is 20 to 99 weight percent based on 100 weight percent of the total weight of the blend. The base layer is co-extruded onto a surface of the functional surface layer and is formed from a polymeric material, wherein the polymeric material is a thermoplastic polyolefin, an aromatic polymer, a polyamide polymer, a polyethylene copolymer, or a combination thereof. The adhesive layer is co-extruded and formed on a surface of the base layer away from the functional surface layer. The adhesive layer is formed from a low-temperature heat-sealable material, wherein the low-temperature heat-sealable material is a metallocene polyolefin, an olefin copolymer, a polyolefin resin, or a combination thereof.

According to the aforementioned polymethylpentene film, the functional material in the functional surface layer has a first melt index, the polymer material in the base layer has a second melt index, and the low-temperature heat-sealable material in the adhesive layer has a third melt index. Furthermore, the difference between the largest and smallest values of the first, second, and third melt indices may be less than 20.

According to the aforementioned polymethylpentene film, the polyolefin resin in the functional surface layer may be polyvinyl chloride, polyethylene, polypropylene, polybutylene, polybutadiene, or a combination thereof.

According to the aforementioned polymethylpentene film, in the base layer, the thermoplastic polyolefin may be polyvinyl chloride, polyethylene, polypropylene, polybutylene, polybutadiene, polymethylpentene, a thermoplastic elastomer, a polyolefin elastomer, or a combination thereof; the aromatic polymer may be polystyrene; the polyamide polymer may be polyamide; and the polyethylene copolymer may be ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-butyl acrylate copolymer, or a combination thereof.

According to the aforementioned polymethylpentene film, in the adhesive layer, the metallocene polyolefin may be an ethylene/α-olefin copolymer, a propylene/α-olefin copolymer, an ethylene/propylene/α-olefin terpolymer, or a combination thereof; and the olefinic copolymer may be an ionic copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-butyl acrylate copolymer, or a combination thereof.

According to the aforementioned polymethylpentene film, the adhesive layer may have an adhesive strength of not less than 20g/15mm.

The aforementioned polymethylpentene film may further include a barrier layer, which is disposed between the functional surface layer and the base layer or between the base layer and the adhesive layer.

According to the aforementioned polymethylpentene film, a material composition of the barrier layer can be an ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyamide, polyvinyl alcohol, or a combination thereof.

Another aspect of the present invention provides a method for preparing a film-coated paper-plastic substrate, comprising providing the polymethylpentene film described in the preceding paragraph, performing a heating step, and performing a laminating step. The heating step involves heating the polymethylpentene film to 300°C to 750°C for 2 to 30 seconds to obtain a softened polymethylpentene film. The laminating step involves laminating the softened polymethylpentene film to a fiber base layer via an adhesive layer to obtain a film-coated paper-plastic substrate.

According to the aforementioned method for preparing the coated paper-plastic substrate, the coating method can be a vacuum suction method or a hot air blowing method.

Another aspect of the present invention provides a film-coated paper-plastic substrate produced by the film-coated paper-plastic substrate preparation method described in the preceding paragraph, wherein the thickness of the fiber base layer can be at least 50% of the overall thickness of the film-coated paper-plastic substrate.

100,310: Polymethylpentene film

110,311: Function layer

120,312: Base layer

130,313: Adhesive layer

200: Preparation method of coated paper-plastic substrate

210, 220, 230: Steps

300:Laminated paper-plastic substrate

320: Fiber basal layer

To make the above and other objects, features, advantages, and embodiments of the present invention more clearly understood, the accompanying drawings are described as follows: Figure 1 is a schematic diagram illustrating a polymethylpentene film according to one embodiment of the present invention; Figure 2 is a flow chart illustrating a method for preparing a coated paper-plastic substrate according to another embodiment of the present invention; and Figure 3 is a schematic diagram illustrating a coated paper-plastic substrate according to yet another embodiment of the present invention.

Several embodiments of the present invention are described below with reference to the accompanying drawings. For the sake of clarity, many practical details are included in the following description. However, it should be understood that these practical details should not be construed to limit the present invention. In other words, these practical details are not essential to some embodiments of the present invention. Furthermore, to simplify the drawings, some commonly used structures and components are shown in simplified schematic form in the drawings; and repeated components may be represented by the same reference numerals.

Please refer to Figure 1, which shows a schematic diagram of a polymethylpentene film 100 according to one embodiment of the present invention. The polymethylpentene film 100 is a multi-layer structure formed by co-extrusion, including a functional surface layer 110, a base layer 120, and an adhesive layer 130.

Functional surface layer 110 is formed from a functional material, wherein the functional material is polymethylpentene (TPX) or a blend of polymethylpentene and a polyolefin resin. The monomers of the polyolefin resin are C2-C4 olefin molecules, and the content of polymethylpentene in the blend is 20 to 99 weight percent, based on 100 weight percent of the total weight of the blend. The polyolefin resin can be polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polybutene (PB), polybutadiene (PB), or a combination thereof. The functional material has a first melt flow index (MFI) ranging from 0.5 to 50, preferably from 1 to 30. Polymethylpentene has a melting point of approximately 220°C to 240°C, making it far more heat-resistant than common film materials such as polyethylene, polypropylene, polylactic acid (PLA), and polyethylene terephthalate (PET). It also has low surface tension, repelling oil and pollutants and exhibiting non-stick properties. The functional surface layer 110 contains sufficient polymethylpentene, making it the most resistant to high-temperature hot oils within the polymethylpentene film 100. The thickness of the functional surface layer 110 can range from 5μm to 90μm.

The base layer 120 is co-extruded onto a surface of the functional surface layer 110 and is formed from a polymer material, wherein the polymer material is a thermoplastic polyolefin, an aromatic polymer, a polyamide polymer, a polyethylene copolymer, or a combination thereof. Furthermore, the thermoplastic polyolefin may be polyvinyl chloride, polyethylene, polypropylene, polybutylene, polybutadiene, polymethylpentene, a thermoplastic elastomer (TPE), a polyolefin elastomer (POE), or a combination thereof. The aromatic polymer may be polystyrene (PS), the polyamide polymer may be polyamide (PA), and the polyethylene copolymer may be ethylene acrylic acid (EAA), ethylene methacrylic acid (EMAA), ethylene butyl acrylate (EBA), or a combination thereof.

The base layer 120 is heat-resistant and adheres well to the functional surface layer 110 and the adhesive layer 130, allowing the functional surface layer 110 and the adhesive layer 130 to adhere to each other through the base layer 120 to form the multi-layered polymethylpentene film 100. The base layer 120 has a second melt index, which can range from 0.5 to 50, preferably from 1 to 30. Furthermore, the base layer 120 provides stiffness and toughness. When filled to a certain thickness, it can make the polymethylpentene film 100 resistant to vacuum pulling. The thickness of the base layer 120 can range from 5μm to 90μm.

Polymethylpentene's low surface tension makes it difficult to mix with other materials and difficult to process. Therefore, conventional films made of polymethylpentene are mostly single-layer structures. The functional material of the functional surface layer 110 of the polymethylpentene film 100 of the present invention is polymethylpentene or a blend of polymethylpentene and a polyolefin resin. By combining it with a base layer 120 that is adhesive to the functional surface layer 110, it can subsequently be fabricated into a multi-layer structure.

Adhesive layer 130 is co-extruded onto a surface of base layer 120 that is distal from functional surface layer 110. Adhesive layer 130 is formed from a low-temperature heat-sealable material, wherein the low-temperature heat-sealable material is a metallocene polyolefin, an olefin copolymer, a polyolefin resin, or a combination thereof. Furthermore, the metallocene polyolefin can be an ethylene/α-olefin copolymer, a propylene/α-olefin copolymer, an ethylene/propylene/α-olefin terpolymer, or a combination thereof. The olefin copolymer can be an ionic copolymer, ethylene-vinyl acetate (EVA), ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-butyl acrylate copolymer, or a combination thereof. Adhesive layer 130 has a third melt index, which may be between 0.5 and 50, preferably between 1 and 30. Adhesive layer 130 exhibits low-temperature adhesion to paper and has an adhesive strength of not less than 20g/15mm. Therefore, polymethylpentene film 100 can be bonded to a fiber substrate (not shown) via adhesive layer 130. Adhesive layer 130 may have a thickness of 5μm to 90μm.

Furthermore, the difference between the largest and smallest values of the first melt index of the functional material in the functional surface layer 110, the second melt index of the polymer material in the base layer 120, and the third melt index of the low-temperature heat-sealable material in the adhesive layer 130 can be less than 20. This ensures that the materials in the functional surface layer 110, base layer 120, and adhesive layer 130 have similar fluidity. When the polymethylpentene film 100 is manufactured by co-extrusion, the similar flow rates between the different layers ensure that the resulting polymethylpentene film 100 has good quality and appearance.

Furthermore, the polymethylpentene film 100 may further include a barrier layer (not shown). The barrier layer is disposed between the functional surface layer 110 and the base layer 120 or between the base layer 120 and the adhesive layer 130. The barrier layer may be composed of ethylene vinyl silane (EVOH), polyvinyl dichloride (PVDC), polyamide (PA), polyvinyl alcohol (PVA), or a combination thereof. The barrier layer effectively blocks gases, particularly oxygen, carbon dioxide, and nitrogen. The ethylene content of the EVOH copolymer is preferably 27 to 45 mol%. However, the material composition of the barrier layer is merely exemplary and not limited to the aforementioned materials; other materials with high gas barrier properties may also be used.

Furthermore, the number of layers in the base layer 120 can be more than one. By combining different polymer materials in the base layer 120, the polymethylpentene film 100 can be designed to meet different functional requirements. The polymethylpentene film 100 can have a multi-layer structure of four, five, or six or more layers. However, the present invention is not limited to this. The number of layers in the polymethylpentene film 100 can be increased or decreased as needed.

Please refer to Figure 2 and Figure 3. Figure 2 illustrates a flow chart of the steps of a method 200 for preparing a coated paper-plastic substrate according to another embodiment of the present invention. Figure 3 illustrates a schematic diagram of a coated paper-plastic substrate 300 according to yet another embodiment of the present invention. The method 200 for preparing a coated paper-plastic substrate includes steps 210, 220, and 230.

Step 210 involves providing a polymethylpentene film 310, which comprises at least a functional surface layer 311, a base layer 312, and an adhesive layer 313. The functional surface layer 311, base layer 312, and adhesive layer 313 of the laminated paper-plastic substrate 300 in Figure 3 are identical to the functional surface layer 110, base layer 120, and adhesive layer 130 of the polymethylpentene film 100 in Figure 1, so the technical details are not further described here. Specifically, the polymethylpentene film 310 can be mounted on the conveyor shaft of a laminating machine. The film is then pulled out and placed on a film clamping frame. When the film clamping frame is raised to a certain height, a heating box slides parallel to the film clamping frame to move above it.

Step 220 is a heating step, in which the polymethylpentene film 310 is heated to 300°C to 750°C for 2 to 30 seconds to obtain a softened polymethylpentene film. The softened polymethylpentene film has formability and adhesiveness.

Step 230 is the laminating step, in which the softened polymethylpentene film is bonded to the fibrous base layer 320 via the adhesive layer 313 to form the laminated paper plastic substrate 300. The low-temperature heat-sealable material in the adhesive layer 313 of the polymethylpentene film 310 embeds itself into the interfiber spaces of the fibrous base layer 320, achieving excellent adhesion and firmly bonding the polymethylpentene film 310 to the fibrous base layer 320. Lamination can be performed using either vacuum suction or hot air pressure. Specifically, after the polymethylpentene film 310 is heated to 300°C to 750°C and maintained for 2 to 30 seconds to obtain a softened polymethylpentene film, the film clamping frame descends vertically onto the workbench. At this time, the cavity below the workbench begins to work and generates negative pressure suction, which adheres the softened polymethylpentene film to the fiber base layer 320. Alternatively, the softened polymethylpentene film can be directly adhered to the fiber of the paper plastic container. The polymethylpentene film 310 includes a base layer 312, which provides stiffness and toughness to the polymethylpentene film 310. This allows the polymethylpentene film 310 to withstand vacuum drawing during the lamination step and maintain a certain thickness. Even if the surface of the fiber base layer 320 is uneven, it is unlikely to become thinner or incompletely coated during vacuum drawing. Consequently, the coated paper-plastic substrate 300 and the coated paper-plastic container produced by the method 200 for preparing a coated paper-plastic substrate exhibit excellent properties such as heat resistance and resistance to hot oil permeation.

The fiber base layer 320 is made of a fiber material that meets food safety requirements and exhibits excellent elasticity and toughness. The thickness of the fiber base layer 320 can be at least 50% of the overall thickness of the coated paper-plastic substrate 300, providing support and shaping for subsequent food packaging. Fiber materials of varying thicknesses and weights can be selected based on usage and requirements.

Accordingly, the coated paper-plastic substrate 300 can be used to manufacture coated paper-plastic containers. These containers exhibit excellent heat resistance and resistance to hot oil permeation. When filled with food, especially sticky rice or noodles, they resist sticking. Their excellent heat resistance also prevents the release of harmful substances such as plasticizers and degradation products, ensuring high food safety. Depending on the application, the coated paper-plastic containers can be shaped like boxes, bags, cups, plates, bowls, or cans. They can be used for sealed food packaging, microwaveable food packaging, modified atmosphere packaging (MAP), fresh food packaging, and general food packaging.

Specifically, please refer to Table 1 below, which shows the polymethylpentene films of the present invention prepared using different formulations, including the component ratios of the polymethylpentene films of Examples 1 to 3 and the films of Comparative Examples 1 to 5, as well as their melt index and adhesive strength. The melt index was tested according to ASTM D1238, and the adhesive strength was tested according to ASTM D903-98. The materials used in the following test examples are as follows: polymethylpentene (MX002), polyolefin resin (C7100), metallocene polyolefin (FV402), polypropylene (Y101), polyethylene (CE4043), adhesive polypropylene (551T), polyamide (NY-B40LN09), ethylene vinyl acetate copolymer (EVA UE633), ionic copolymer (Surlyn 1652SR), polyethylene terephthalate (DryStar 0603PETG), and polylactic acid (HZ-200).

The comparison results in Table 1 show that the film prepared in Comparative Example 1, which is composed solely of polymethylpentene, lacks adhesive properties. However, the polymethylpentene films of Examples 1, 2, and 3 of the present invention all exhibit excellent adhesive strength, overcoming the shortcomings of polymethylpentene materials and facilitating subsequent processing or lamination onto fiber-based paper-plastic containers.

In the experiments, the polymethylpentene film of Example 1 was further prepared into a coated paper-plastic substrate using the method for preparing a coated paper-plastic substrate of the present invention, and the coated paper-plastic container of Example 4 was further prepared. Furthermore, the films of Comparative Examples 2 to 5 were prepared using the same method to prepare coated paper-plastic containers of Comparative Examples 6 to 9. These containers were then tested for heat resistance (including resistance to hot water and hot oil), microwave or oven heating, food non-stick properties, food hygiene safety, and resistance to deformation upon heating.

Hot water resistance is tested according to GB/T36787-2018 6.6.1; hot oil resistance is tested according to GB/T36787-2018 6.6.2 Test: Whether it can be microwaved: heat the coated plastic container at 1440W for 1 minute and observe the oil seepage of the coated plastic container. If there is no oil seepage, it indicates an excellent result. If there is oil seepage, it is further classified into good result, acceptable result and poor result according to the oil seepage. Whether it can be oven-heated: heat the coated plastic container in an oven at 180℃ for 5 minutes and observe whether there is oil seepage and deformation of the coated plastic container. If there is no oil seepage and deformation, it indicates an excellent result. If there is oil seepage and deformation, it is further classified into good result, acceptable result and poor result according to the oil seepage and deformation. Food non-stickiness is tested by the blocking test according to the alliance company method. Put sticky food into the container and observe whether the coated paper and plastic container sticks to the food. If there is no sticking, the result is excellent. If there is sticking, it is further classified into good results, acceptable results, and poor results based on the sticking situation. Food hygiene and safety are tested according to the Food Utensil Container Packaging Hygiene Standard No. 1111303439 of the Ministry of Health. Heat deformation resistance is tested according to the Hygiene and Welfare Standard. The test was conducted according to the Ministry of Health and Welfare's Food Administration Method No. 1061902219. Freeze resistance was tested according to the Alliance Company's method: the coated paper-plastic container was placed at -40°C for 24 hours and then dropped from a height of 1.5 meters at -40°C. No film damage was considered an excellent result. If film damage was present, the test was further categorized as good, acceptable, or poor based on the damage. Table 2 below shows the test results for the coated paper-plastic container of Example 4 and Comparative Examples 6 to 9. A ◎ indicates an excellent result, a ○ indicates a good result, a △ indicates an acceptable result, and an × indicates a poor result.

In terms of hot water resistance, the coated paper-plastic containers of Comparative Examples 7, 8, and Example 4 achieved excellent results. In food hygiene and safety testing, the coated paper-plastic containers of Comparative Examples 7 and Example 4 showed no plasticizer release. In terms of freeze resistance, the coated paper-plastic containers of Comparative Examples 6, 8, and Example 4 achieved excellent results. However, in testing for hot oil resistance, microwaveability, ovenability, food non-stickiness, and heat deformation resistance, only the coated paper-plastic container of Example 4 achieved excellent results. The test results in Table 2 demonstrate that the coated paper-plastic container of Example 4 exhibits excellent performance in terms of hot water resistance, hot oil resistance, food non-stick properties, food hygiene and safety, heat deformation resistance, and freeze resistance. Furthermore, it can be heated in a microwave oven and oven. Therefore, the coated paper-plastic container made with the coated paper-plastic substrate of the present invention can be used to hold a variety of foods, such as ready-to-eat foods, which can be refrigerated or frozen and then heated in a microwave oven or oven. Upon heating, the coated paper-plastic container exhibits minimal heat deformation and provides a heat-insulating effect, making it easier for users to hold. Furthermore, because the coated paper-plastic substrate of the present invention exhibits food non-stick properties, the resulting container prevents sticking or residue even when used to hold sticky foods such as rice and noodles. Because the coated paper-plastic substrate of the present invention is heat-resistant to hot water and hot oil, the resulting coated paper-plastic container is particularly suitable for holding foods containing hot soup or hot oil, eliminating the need for plastic bags. It can also safely replace existing coated paper-plastic containers made of film materials, providing an environmentally friendly, safe, and hygienic solution with significant advantages in terms of food safety and human health.

The hot oil permeability resistance of the coated paper-plastic container of Example 4 was further tested under different heating conditions in an oven, microwave, and steamer. The test conditions are shown in Table 3 below. For the oven and microwave heating tests, 200 mL of salad oil was poured into the coated paper-plastic container of Example 4 and the container was inspected after the test period to see if any oil had seeped into it. For the steamer heating test, prepared food was placed into the coated paper-plastic container of Example 4 and the container was inspected after the test period to see if any oil had seeped into it.

The test results in Table 3 show that when heated in an oven at 160°C, hot oil still did not penetrate the coated paper-plastic container of Example 4; when heated in a microwave oven at a heating power of 1440W, hot oil still did not penetrate the coated paper-plastic container of Example 4; and when heated in a steamer at a temperature as high as 220°C, no hot oil was observed to penetrate the coated paper-plastic container of Example 4. This demonstrates that coated paper-plastic containers made with the coated paper-plastic substrate of the present invention have excellent resistance to hot oil permeation and are therefore suitable for holding hot food or heating the contained food in a microwave oven, oven, or steamer.

Although the present invention has been disclosed above in terms of embodiments, this is not intended to limit the present invention. Anyone skilled in the art may make various modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

100: Polymethylpentene film 110: Functional surface layer 120: Base layer 130: Adhesive layer

Claims (10)

A coated paper-plastic substrate comprises: A polymethylpentene film comprising: A functional surface layer formed from a functional material, wherein the functional material is polymethylpentene or a blend of the polymethylpentene and a polyolefin resin, wherein a monomer of the polyolefin resin is a C2-C4 olefin molecule, and the content of the polymethylpentene in the blend is 20 weight percent to 99 weight percent based on 100 weight percent of the total weight of the blend; A base layer formed by co-extrusion on a surface of the functional surface layer, wherein the base layer is formed from a polymeric material, wherein the polymeric material is a thermoplastic polyolefin, an aromatic polymer, a polyamide polymer, a polyethylene copolymer, or a combination thereof; and An adhesive layer is co-extruded on a surface of the base layer remote from the functional surface layer. The adhesive layer is formed from a low-temperature heat-sealable material, wherein the low-temperature heat-sealable material is a metallocene polyolefin, an olefin copolymer, the polyolefin resin, or a combination thereof, and has an adhesive strength of not less than 20 g/15 mm. A fiber base layer is provided, the polymethylpentene film being bonded to the fiber base layer via the adhesive layer. The coated paper-plastic substrate as described in claim 1, wherein the functional material in the functional surface layer has a first melting index, the polymer material in the base layer has a second melting index, the low-temperature heat-sealable material in the adhesive layer has a third melting index, and the difference between the largest value and the smallest value among the first melting index, the second melting index and the third melting index is less than 20. The coated paper-plastic substrate as described in claim 1, wherein in the functional surface layer, the polyolefin resin is polyethylene, polypropylene, polybutylene, polybutadiene or a combination thereof. The coated paper-plastic substrate as described in claim 1, wherein in the base layer, the thermoplastic polyolefin is polyethylene, polypropylene, polybutylene, polybutadiene, polymethylpentene, a thermoplastic elastomer, a polyolefin elastomer or a combination thereof, the aromatic polymer is polystyrene, the polyamide polymer is polyamide, and the polyethylene copolymer is ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene butyl acrylate copolymer or a combination thereof. The coated paper-plastic substrate as described in claim 1, wherein in the adhesive layer, the metallocene polyolefin is an ethylene/α-olefin copolymer, a propylene/α-olefin copolymer, an ethylene/propylene/α-olefin terpolymer, or a combination thereof, and the olefinic copolymer is an ionic copolymer, an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ethylene-butyl acrylate copolymer, or a combination thereof. The coated paper-plastic substrate as described in claim 1, wherein a thickness of the fiber base layer is more than 50% of the overall thickness of the coated paper-plastic substrate. The laminated paper-plastic substrate as described in claim 1 further comprises a barrier layer, which is disposed between the functional surface layer and the base layer or between the base layer and the adhesive layer. The laminated paper-plastic substrate as described in claim 7, wherein a material of the barrier layer is composed of an ethylene-vinyl alcohol copolymer, a polyvinylidene chloride, a polyamide, a polyvinyl alcohol or a combination thereof. A method for preparing a film-coated paper-plastic substrate comprises: providing a polymethylpentene film, the polymethylpentene film comprising: a functional surface layer formed from a functional material, wherein the functional material is polymethylpentene or a blend of the polymethylpentene and a polyolefin resin, wherein a monomer of the polyolefin resin is a C2-C4 olefin molecule, and the content of the polymethylpentene in the blend is 20 to 99 weight percent based on 100 weight percent of the total weight of the blend; a base layer formed by co-extrusion on a surface of the functional surface layer, the base layer being formed from a polymeric material, wherein the polymeric material is a thermoplastic polyolefin, an aromatic polymer, a polyamide polymer, a polyethylene copolymer, or a combination thereof; and an adhesive layer formed by co-extrusion on a surface of the base layer away from the functional surface layer, the adhesive layer being formed from a low-temperature heat-sealable material, wherein the low-temperature heat-sealable material is a metallocene polyolefin, an olefin copolymer, the polyolefin resin, or a combination thereof, and the adhesive layer having an adhesive strength of not less than 20 g/15 mm; and performing a heating step to heat the polymethylpentene film to a temperature between 300 ^° C and 750 ^°C. C is maintained for 2 seconds to 30 seconds to obtain a softened polymethylpentene film; and a laminating step is performed to adhere the softened polymethylpentene film to a fiber base layer through the adhesive layer in a laminating manner to obtain a laminated paper-plastic substrate. The method for preparing a coated paper-plastic substrate as described in claim 9, wherein the coating method is a vacuum suction method or a hot air blowing method.