Food packaging material and method for manufacturing the same

Abstract

To provide a food packaging material and a method for manufacturing the same.SOLUTION: This food packaging material comprises: a cast polypropylene layer; a heat-proof surface layer; and an intermediate layer laid between the heat-proof surface layer and the cast polypropylene layer. A material for the cast polypropylene layer contains a first propylene copolymer, a material for the heat-proof surface layer contains a propylene homopolymer and a petroleum resin, and a material for the intermediate layer contains a second propylene copolymer. A melting point of the heat-proof surface layer is higher than that of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than that of the intermediate layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a food packaging material and a method for manufacturing the same, and particularly to a food packaging material suitable for heat-seal packaging or vacuum packaging and a method for manufacturing the same.

Background Art

[0002] Many of the currently commercially available food packaging materials are composed of multiple materials such as a polyester layer, an aluminum foil layer, and a polypropylene layer. Since food packaging materials cannot be directly recycled due to differences in materials, a large amount of disposable waste is likely to be generated, and concerns about environmental problems are increasing.

[0003] When combining different types of materials, it is usually necessary to use an adhesive. In addition to the problem that the manufacturing process becomes complicated in the process of applying the adhesive to the layer, the solvent used in the adhesive can also cause environmental pollution. In the long run, such food packaging materials are considered to be disadvantageous for environmental protection.

[0004] On the other hand, a food packaging material made of a single material has the advantage that it can be directly recovered and reused, but its physical properties are usually inferior to those of a food packaging material composed of a plurality of materials combined.

[0005] Therefore, manufacturing a food packaging material made of a single material while maintaining good physical properties through improvements in materials and structures has become an important issue for this business.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technical problem to be solved by the present invention is to provide a food packaging material and a method for manufacturing the same in view of the deficiencies of the prior art.

Means for Solving the Problems

[0007] To solve the above technical problems, one of the technical means employed by the present invention is to provide a food packaging material. The food packaging material comprises a cast polypropylene layer, a heat-resistant surface layer, and an intermediate layer placed between the heat-resistant surface layer and the cast polypropylene layer. The material of the cast polypropylene layer contains a first propylene copolymer, the material of the heat-resistant surface layer contains a propylene homopolymer and a petroleum resin, and the material of the intermediate layer contains a second propylene copolymer. The melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer.

[0008] In one embodiment, the melting point of the propylene homopolymer is 160°C to 170°C.

[0009] In one embodiment, the melting point of the first propylene copolymer is 145°C to 159°C.

[0010] In one embodiment, the melting point of the second propylene copolymer is 125°C to 140°C.

[0011] In one embodiment, in the heat-resistant surface layer, if the total weight of propylene homopolymer, petroleum resin, and inorganic filler is 100% by weight, the content of propylene homopolymer is 87% to 94% by weight, and the content of petroleum resin is 1.5% to 5% by weight.

[0012] In one embodiment, if the total weight of the first propylene copolymer is 100% by weight, the first propylene copolymer is obtained by polymerizing 90% to 99.99% by weight of propylene monomer and 0.01% to 10% by weight of ethylene monomer.

[0013] In one embodiment, if the total weight of the second propylene copolymer is 100% by weight, the second propylene copolymer is obtained by polymerizing 70% to 85% by weight of propylene monomer and 15% to 30% by weight of ethylene monomer.

[0014] In one embodiment, the petroleum resin is a hydrogenated petroleum resin having 5 or 10 carbon atoms.

[0015] In one embodiment, the petroleum resin is an aromatic copolymer hydrogenated petroleum resin formed by the reaction of a hydrogenated petroleum resin having 5 or 10 carbon atoms with an aromatic compound.

[0016] In one embodiment, the hydrogenated petroleum resin having 5 or 10 carbon atoms is a piperylene hydrogenated resin or a dicyclopentadiene hydrogenated resin.

[0017] In one embodiment, the thickness of the intermediate layer is 18 μm to 20 μm, the thickness of the cast polypropylene layer is 50 μm to 70 μm, and the thickness of the heat-resistant surface layer is 20 μm to 30 μm.

[0018] To solve the above technical problems, another technical means employed by the present invention is to provide a method for manufacturing food packaging materials. The method for manufacturing food packaging materials includes a casting step of forming a cast polypropylene layer, a biaxial stretching step of forming a laminated structure, and a step of manufacturing food packaging materials by placing the cast polypropylene layer in the laminated structure. The laminated structure comprises an intermediate layer and a heat-resistant surface layer, and the cast polypropylene layer is in contact with the intermediate layer. The material of the cast polypropylene layer includes a first propylene copolymer. The material of the intermediate layer includes a second propylene copolymer. The material of the heat-resistant surface layer includes a propylene homopolymer, petroleum resin, and an inorganic filler. The melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer. [Effects of the Invention]

[0019] One of the advantageous effects of the present invention is that, due to the technical features of the food packaging material and its manufacturing method according to the present invention, "the material of the heat-resistant surface layer includes propylene homopolymer, petroleum resin, and inorganic filler" and "the melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer," the food packaging material can achieve both the convenience of being directly recyclable and good physical properties. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic side view of the food packaging material according to the present invention. [Modes for carrying out the invention]

[0021] To further understand the features and technical details of this invention, please refer to the following detailed description of the invention and the accompanying drawings. However, the accompanying drawings provided are for reference and illustrative purposes only and do not limit the scope of the claims of this invention.

[0022] The following describes a "food packaging material and method for manufacturing the same" according to an embodiment of the present invention, and those skilled in the art will be able to understand the advantages and effects of the present invention based on the contents disclosed herein. The present invention can be carried out or applied by other different specific embodiments, and various modifications and changes can be made to each detail herein, based on different viewpoints and uses, as long as they do not deviate from the concept of the present invention. It should also be noted in advance that the accompanying drawings of the present invention are for simple schematic explanation and are not drawn to actual size. The technical content of the present invention will be described in more detail below based on the embodiments, but the scope of protection of the present invention is not limited by the contents disclosed herein. The term "or" as used herein may include any one or more combinations of the items listed in relation to the actual situation.

[0023] In order to overcome the drawback that the types of materials of conventional food packaging materials are complex and cannot be directly recycled, according to the present invention, a food packaging material made of a single material is developed.

[0024] The food packaging material according to the present invention employs polypropylene as the main component. Even though it has the characteristic of being a single material, the food packaging material according to the present invention still has quite excellent physical properties (high tensile strength, low shrinkage rate, high heat resistance).

[0025] In order to achieve good physical properties, the food packaging material according to the present invention has a multi-layer structure. The design concept is to sandwich the layer with a low melting point by two layers with a high melting point, so as to improve the heat resistance while maintaining the flexibility of the food packaging material.

[0026] Also, the melting points of the two layers serving as the outer layers are also different (the difference in their melting points may be 5°C to 25°C). Thus, the food packaging material performs a heat-sealing process at an appropriate temperature and is used as a heat-sealing material. Therefore, the food packaging material of the present invention has a wider packaging application range and can replace the conventional food packaging materials that cannot be directly recycled.

[0027] In order to adjust to have different characteristics based on the same material, in the present invention, by adjusting the types and blending ratios of monomers or blending other components, different melting point ranges of the layers are obtained, so that ideal characteristics can be obtained.

[0028] As shown in FIG. 1, the food packaging material 1 of the present invention has a three-layer structure. The food packaging material 1 includes a cast polypropylene layer 10, a heat-resistant surface layer 20, and an intermediate layer 30. The intermediate layer 30 is installed between the cast polypropylene layer 10 and the heat-resistant surface layer 20.

[0029] In one exemplary embodiment, the cast polypropylene layer 10 is fixed onto the intermediate layer 30 via an adhesive, and the heat-resistant surface layer 20 and the intermediate layer 30 are integrally molded; however, the present invention is not limited thereto. The specific manufacturing processes for the cast polypropylene layer 10, the heat-resistant surface layer 20, and the intermediate layer 30 are described below.

[0030] The cast polypropylene layer 10 is the inner surface of the food packaging material 1 and is the main surface that comes into contact with food. In one preferred embodiment, the cast polypropylene layer 10 is formed from a single component and does not contain any other materials or additives. In some applications, the cast polypropylene layer 10 is also used as a heat seal layer. That is, the melting point of the cast polypropylene layer 10 is lower than the melting point of the heat-resistant surface layer 20, so that when the heat-sealing process is performed on the cast polypropylene layer 10, the heat-resistant surface layer 20 can maintain its original shape and condition.

[0031] The material of the cast polypropylene layer 10 includes a first propylene copolymer. The melting point of the first propylene copolymer is 145°C to 159°C, preferably 147°C to 155°C. The melting point of the first propylene copolymer may also be 148°C, 149°C, 150°C, 151°C, 152°C, 153°C, or 154°C. Experimental measurements showed that the melt flow index (MI) of the first propylene copolymer was 5 g / 10 min to 10 g / 10 min (under measurement conditions of 230°C and 2.16 kg).

[0032] Since the cast polypropylene layer 10 is formed by casting and does not undergo a stretching process, the cast polypropylene layer 10 can have relatively good heat resistance and transparency.

[0033] The first propylene copolymer is obtained by copolymerizing a propylene monomer and an ethylene monomer. Assuming the total weight of the first propylene copolymer is 100% by weight, the first propylene copolymer is obtained by polymerizing 90% to 99.99% by weight of propylene monomer and 0.01% to 10% by weight of ethylene monomer. For example, the propylene monomer content may be 92 wt%, 94 wt%, 96 wt%, or 98 wt%, and the ethylene monomer content may be 1 wt%, 2 wt%, 4 wt%, 6 wt%, 8 wt%, or 9 wt%. During the polymerization process, the ethylene monomer is randomly mixed between the propylene monomers, which can lower the crystallinity and melting point of the first propylene copolymer. However, the toughness, impact resistance, oxidation (deterioration) resistance, and long-term heat resistance of the first propylene copolymer are all improved by adding a small amount of ethylene monomer.

[0034] The heat-resistant surface layer 20 is the outer surface of the food packaging material 1 and is exposed to the external environment for extended periods. Furthermore, the heat-resistant surface layer 20 is the layer with the best heat resistance in the food packaging material 1 and has the highest melting point. Therefore, when performing a heat-sealing process on the food packaging material 1, the heat-sealing temperature must not exceed the melting point of the heat-resistant surface layer 20.

[0035] The material of the heat-resistant surface layer 20 includes propylene homopolymer, petroleum resin, and inorganic filler, with propylene homopolymer being the main component (i.e., its content is more than 70% by weight).

[0036] Compared to propylene copolymers, propylene homopolymers have a relatively regular molecular arrangement, and therefore possess a relatively high melting point. Specifically, the melting point of propylene homopolymers is 160°C to 170°C, preferably 165°C to 168°C. For example, the melting point of the first propylene copolymer may be 166°C or 167°C. Experimental measurements showed that the melt flow index of propylene homopolymers was 2 g / 10 min to 3 g / 10 min (measured at 230°C and 2.16 kg).

[0037] The addition of petroleum resin improves the crystallinity of the amorphous phase of the propylene homopolymer, and further improves the melting point and rigidity of the propylene homopolymer. Preferably, the petroleum resin is hydrogenated petroleum resin (also called hydrogenated resin). The hydrogenated petroleum resin not only imparts appropriate crystallinity to the propylene homopolymer, but also plays a role in thickening and reinforcing, thereby improving the mechanical and optical properties of the propylene homopolymer and giving the heat-resistant surface layer 20 desirable heat resistance.

[0038] For example, the petroleum resin may be a hydrogenated petroleum resin having 5 or 10 carbon atoms. For example, the petroleum resin may be a piperine hydrogenated resin or a dicyclopentadiene (DCPD) hydrogenated resin. In one embodiment, a hydrogenated petroleum resin having 5 or 10 carbon atoms may be further reacted with an aromatic to produce an aromatic copolymerized hydrogenated petroleum resin. The aromatic copolymerized hydrogenated petroleum resin can be given excellent heat resistance by the heat-resistant surface layer 20.

[0039] The addition of inorganic fillers is intended to prevent the layers from blocking during the manufacturing process, which would affect quality. The inorganic fillers may be silicon dioxide, for example, silicon dioxide with a size of 2 μm to 15 μm. In one exemplary example, two inorganic fillers with two particle sizes may be used in combination, for example, silicon dioxide with a particle size of 1 μm to 3 μm and silicon dioxide with a particle size of 3.1 μm to 5 μm.

[0040] In one exemplary example, if the total weight of propylene homopolymer, petroleum resin, and inorganic filler is 100% by weight, the content of propylene homopolymer is 87% to 94% by weight, the content of petroleum resin is 1.5% to 5% by weight, and the content of inorganic filler is 0.03% to 0.15% by weight. For example, the content of propylene homopolymer may be 88%, 89%, 90%, 91%, 92%, or 93% by weight.

[0041] The intermediate layer 30 acts as a flexible, bendable layer in the food packaging material 1, providing convenience in its use. The intermediate layer 30 is placed between the cast polypropylene layer 10 and the heat-resistant surface layer 20, and the intermediate layer 30 has the lowest melting point in the food packaging material 1. That is, the melting point of the heat-resistant surface layer 20 is higher than that of the cast polypropylene layer 10, and the melting point of the cast polypropylene layer 10 is higher than that of the intermediate layer 30.

[0042] The material of the intermediate layer 30 includes a second propylene copolymer and may selectively contain inorganic fillers, wherein the second propylene copolymer is the main component (i.e., the content is greater than 70% by weight).

[0043] The melting point of the second propylene copolymer is 125°C to 140°C, preferably 130°C to 133°C. The melting point of the second propylene copolymer may also be 131°C or 132°C. Experimental measurements show that the melt flow index of the first propylene copolymer is 5 g / 10 min to 7 g / 10 min (under measurement conditions of 230°C and 2.16 kg).

[0044] The second propylene copolymer is obtained by copolymerizing a propylene monomer and an ethylene monomer. Assuming the total weight of the second propylene copolymer is 100% by weight, the second propylene copolymer is obtained by polymerizing 70% to 85% by weight of propylene monomer and 15% to 30% (wt%) by weight of ethylene monomer. For example, the propylene monomer content may be 72 wt%, 74 wt%, 76 wt%, 78 wt%, 80 wt%, 82 wt%, or 84 wt%, and the ethylene monomer content may be 16 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 26 wt%, or 28 wt%.

[0045] Simply put, by adjusting the types and structures of microscopic molecules, it is possible to impart different melting points to polypropylene materials and control the properties of the layers. The melting point of the propylene homopolymer is higher than that of the first propylene copolymer, and the melting point of the first propylene copolymer is higher than that of the second propylene copolymer. Therefore, the melting point of the heat-resistant surface layer 20 is higher than that of the cast polypropylene layer 10, and furthermore, the melting point of the cast polypropylene layer 10 is higher than that of the intermediate layer 30.

[0046] For ease of use and packaging functionality, the thickness of the cast polypropylene layer 10 is adjusted to be greater than the thickness of the heat-resistant surface layer 20, and the thickness of the heat-resistant surface layer 20 is adjusted to be greater than the thickness of the intermediate layer 30. In one preferred embodiment, the thickness of the intermediate layer is 18 μm to 20 μm, the thickness of the cast polypropylene layer is 50 μm to 70 μm, and the thickness of the heat-resistant surface layer is 20 μm to 30 μm.

[0047] The method for manufacturing food packaging material according to the present invention includes the following steps. First, a cast polypropylene film (CPP film) is manufactured by performing a casting step using the first propylene copolymer. In the casting step, the first propylene copolymer is melted via an extruder and then extruded using a T-shaped die. The molten first propylene copolymer is formed into a sheet on a smoothly rotating roll, and when it hardens by cooling, a cast polypropylene layer is obtained.

[0048] The propylene homopolymer, petroleum resin, and inorganic filler are mixed to form a heat-resistant surface layer material. The second propylene copolymer and inorganic filler are mixed to form an intermediate layer material. Subsequently, the heat-resistant surface layer material and the intermediate layer material are fed into the feed port of a biaxial stretching machine, and after melt extrusion and stretching, a laminated structure is obtained. The laminated structure is integrally molded with the heat-resistant surface layer and the intermediate layer. That is, both the heat-resistant surface layer and the intermediate layer are biaxially oriented polypropylene film (BOPP film). In the actual product, no clear interface is observed between the heat-resistant surface layer and the intermediate layer, but the two are definitely different in terms of composition.

[0049] Next, the food packaging material of the present invention can be manufactured by placing the cast polypropylene layer in a laminated structure and bringing the cast polypropylene layer into contact with the intermediate layer. Since both the cast polypropylene layer and the laminated structure are molded, they can be adhered and fixed with a polyolefin adhesive, but the present invention is not limited to this.

[0050] In one exemplary example, the polyolefin adhesive is prepared from polyolefin colloidal particles, a modifier, a curing agent, and a mixed solvent. The polyolefin particles may be made of propylene random copolymer. The modifier may be selected from the group consisting of maleic anhydride, methyl tetrahydrophthalic anhydride (MTHPA), 3,4,5,6-tetrahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride (THPA), methylhexahydrophthalic anhydride (MHHPA), methyl nadic anhydride (MNA), and 2,3-naphthalenedicarboxylic anhydride. The curing agent may be a polyisocyanate-based curing agent, such as Desmodur® ultra N3300, Desmodur® ultra N3600, or a combination thereof. The mixed solvent contains a non-polar solvent and a polar solvent, and the mass ratio of the non-polar solvent to the polar solvent (non-polar solvent: polar solvent) is 4:1 to 3:2. The non-polar solvent may be methylcyclohexane, cyclohexane, n-hexane, or a combination thereof. The polar solvent may be methyl ethyl ketone, ethyl acetate, methyl isobutyl ketone, n-propyl acetate, or a combination thereof. Preferably, the non-polar solvent is methylcyclohexane, and the polar solvent is methyl ethyl ketone, ethyl acetate, or a mixture thereof.

[0051] It should be noted that the order in which the cast polypropylene layer and the laminated structure are formed is not limited to the above description; the laminated structure may be formed first, followed by the cast polypropylene layer. [Examples]

[0052] To measure the properties of the food packaging material of the present invention, food packaging materials of Example 1 and Comparative Examples 1 and 2 were manufactured based on the above process, and the composition of the materials forming each layer is as shown in Table 1 below. The difference between the examples and comparative examples is that the composition of the heat-resistant surface layer is different. Specifically, Comparative Example 1 does not contain rigidity-improving pellets, and Comparative Example 2 does not contain rigidity-improving pellets and does not use propylene homopolymer as the main component.

[0053] To further clarify, petroleum resin (rigidity-enhancing pellets) and inorganic fillers (anti-tack pellets) may be added in pellet form to ensure uniform mixing of the materials. Specifically, in the rigidity-enhancing pellets, the content of hydrogenated petroleum resin (hydrogenated petroleum resin formed by the reaction of dicyclopentadiene with aromatics) is 30% to 50% by weight, and the content of silicon dioxide in the anti-tack pellets is 3% to 5% by weight. In the examples described later, the content of hydrogenated petroleum resin (hydrogenated petroleum resin formed by the reaction of dicyclopentadiene with aromatics) in the rigidity-enhancing pellets is 50% by weight, and the content of silicon dioxide in the anti-tack pellets is 5% by weight. In Table 1, if expressed as the amount of pellets added, the specific content of petroleum resin or inorganic filler can be obtained by calculation.

[0054] To demonstrate that the food packaging material according to the present invention possesses good properties, the tensile strength of the food packaging material was measured based on the standard measurement method of ASTM D-638. The food packaging material was left to stand at temperatures of 120°C and 150°C for 3 minutes, and its shrinkage rate relative to its original size was measured. Two samples of the food packaging material were taken, heat-sealed for 1 second at a temperature of 180°C and a pressure of 0.2 MPa, and then peeled off at a speed of 300 m / min using a tensile testing machine to measure the heat seal strength. In addition, the temperature at which blocking occurred due to the food packaging material being exposed to heat was recorded to evaluate its heat resistance. The results of the above measurements are shown in Table 1.

[0055] [Table 1]

[0056] As can be seen from the results in Table 1, the food packaging material according to the present invention has relatively excellent tensile strength, and can therefore replace currently available food packaging materials, and furthermore, has the advantage of being directly recyclable. In addition, the food packaging material according to the present invention has a relatively low shrinkage rate and desirable heat resistance (relatively high blocking temperature), and can maintain its original size even at a temperature of 120°C, and shrinks only slightly at a temperature of 150°C. Due to these excellent properties, the food packaging material according to the present invention can be used in a wider range of applications, and in particular can be applied to heat-seal packaging and vacuum packaging.

[0057] [Advantageous effects of the embodiment] One of the advantageous effects of the present invention is that, due to the technical features of the food packaging material and its manufacturing method according to the present invention, "the material of the heat-resistant surface layer includes propylene homopolymer, petroleum resin, and inorganic filler" and "the melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer," the food packaging material can achieve both the convenience of being directly recyclable and good physical properties.

[0058] The information disclosed above represents only preferred and implementable embodiments of the present invention, and the claims of the present invention are not limited thereto. Therefore, any equivalent technical modifications made using the description and drawings of the present invention are all included within the scope of the claims of the present invention. [Explanation of Symbols]

[0059] 1...Food packaging materials 10...Cast polypropylene layer 20...Heat-resistant surface layer 30...Middle class

Claims

1. The material comprises a cast polypropylene layer containing a first propylene copolymer, The material includes a heat-resistant surface layer containing propylene homopolymer, petroleum resin, and silicon dioxide, which is an inorganic filler. A food packaging material comprising an intermediate layer placed between the heat-resistant surface layer and the cast polypropylene layer, and comprising a material containing a second propylene copolymer, The aforementioned petroleum resin is an aromatic copolymer hydrogenated petroleum resin formed by the reaction of dicyclopentadiene with an aromatic compound. The melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer. A food packaging material characterized in that the thickness of the intermediate layer is 18 μm to 20 μm, the thickness of the cast polypropylene layer is 50 μm to 70 μm, and the thickness of the heat-resistant surface layer is 20 μm to 30 μm.

2. The food packaging material according to claim 1, wherein the melting point of the propylene homopolymer is 160°C to 170°C.

3. The food packaging material according to claim 1, wherein the melting point of the first propylene copolymer is 145°C to 159°C.

4. The food packaging material according to claim 1, wherein the melting point of the second propylene copolymer is 125°C to 140°C.

5. The food packaging material according to claim 1, wherein, in the heat-resistant surface layer, if the total weight of the propylene homopolymer, the petroleum resin, and the inorganic filler is 100% by weight, the content of the propylene homopolymer is 87% to 94% by weight, and the content of the petroleum resin is 1.5% to 5% by weight.

6. The food packaging material according to claim 1, wherein, assuming the total weight of the first propylene copolymer is 100% by weight, the first propylene copolymer is obtained by polymerizing 90% to 99.99% by weight of propylene monomer and 0.01% to 10% by weight of ethylene monomer.

7. The food packaging material according to claim 1, wherein, assuming the total weight of the second propylene copolymer is 100% by weight, the second propylene copolymer is obtained by polymerizing 70% to 85% by weight of propylene monomer and 15% to 30% by weight of ethylene monomer.

8. A casting step is performed to form a cast polypropylene layer containing a first propylene copolymer as the material, A biaxial stretching step for forming a laminated structure comprising an intermediate layer containing a second propylene copolymer and a heat-resistant surface layer containing a propylene homopolymer, a petroleum resin, and silicon dioxide as an inorganic filler, wherein the petroleum resin is an aromatic copolymer hydrogenated petroleum resin formed by the reaction of dicyclopentadiene with an aromatic compound, A method for manufacturing food packaging material, comprising the step of manufacturing food packaging material by installing the cast polypropylene layer in the laminated structure, The cast polypropylene layer is in contact with the intermediate layer, The melting point of the heat-resistant surface layer is higher than the melting point of the cast polypropylene layer, and the melting point of the cast polypropylene layer is higher than the melting point of the intermediate layer. A method for manufacturing food packaging material, characterized in that the thickness of the intermediate layer is 18 μm to 20 μm, the thickness of the cast polypropylene layer is 50 μm to 70 μm, and the thickness of the heat-resistant surface layer is 20 μm to 30 μm.

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