Manufacturing method of puncture-resistant low-thermal-shrinkage food-grade high-temperature cooking film

Abstract

The invention discloses a manufacturing method of a puncture-resistant low-thermal-shrinkage food-grade high-temperature cooking film, and relates to the technical field of cooking films, the puncture-resistant low-thermal-shrinkage food-grade high-temperature cooking film comprises an outer layer, a middle layer and an inner layer, and the thickness percentage of the outer layer to the middle layer to the inner layer is 30%: 15%: 55%. By adding the nylon, the fibrous reinforcing agent and the styrene-butadiene thermoplastic elastomer, the puncture resistance and the tensile property of the cooking film are greatly improved, and meanwhile, under the action of external force, the prepared cooking film can keep higher ductility and toughness and is not easy to break.

Description

Technical Field

[0001] The invention relates to the technical field of retorting films, in particular to a method for manufacturing a puncture-resistant, low-heat-shrinkage food-grade high-temperature retorting film. Background Art

[0002] Retort film is a film material specially designed for retort packaging. It can maintain stable performance in a high-temperature retort environment to ensure the quality and safety of the packaged contents. It is mainly used for the packaging of food, medicines and other products that require high-temperature retort treatment. It can withstand changes in temperature, pressure and humidity during the high-temperature retort process while maintaining the integrity and sealing of the package to prevent the contents from being contaminated or deteriorating.

[0003] The defects of existing cooking films are: 1. Patent document US06599639B2 discloses a co-extruded, retortable multilayer film, but the retortable multilayer film in the above document is difficult to use for foods or materials that are heavy and have sharp edges; 2. Patent document US20060172098A1 discloses a retortable / peelable film, but the barrier properties of the retortable film in the above document are poor, and it is difficult to effectively prevent water vapor and oxygen from entering the outer wall; 3. Patent document JP2001064424A discloses a transparent gas barrier film, but the transparent gas barrier film in the above document is difficult to maintain shape stability and material integrity during high temperature cooking tests; 4. Patent document CN113276512B discloses a recyclable cooking bag and a recyclable cooking polyester film. However, in the above document, during the high-temperature cooking process, harmful substances present in the cooking polyester film are easily transferred into the food, resulting in technical problems of unsafe use of the cooking film. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a puncture-resistant, low-heat-shrinkage food-grade high-temperature cooking film to solve the technical problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for manufacturing a puncture-resistant, low-heat-shrinkage food-grade high-temperature cooking film, comprising an outer layer, a middle layer and an inner layer, wherein the thickness percentage of the outer layer, the middle layer and the inner layer is 30%:15%:55%; The mass percentages of the components of the outer layer are 82.2% to 83.8% of ethoxyethyl acrylate, 14.5% to 15.2% of nylon, 1% to 2.7% of fibrous reinforcing agent, and 0.1% to 0.5% of additives; the mass percentages of the components of the middle layer are 76.2% to 76.8% of ethylene-vinyl alcohol copolymer and 23.2% to 23.8% of polyamide; the mass percentages of the components of the inner layer are 83.3% to 83.9% of ethoxyethyl acrylate, 14.3% to 14.8% of styrene-butadiene thermoplastic elastomer, 1.1% to 1.6% of fibrous reinforcing agent, and 0.1% to 0.7% of additives; The steps for making the puncture-resistant, low heat shrinkage food-grade high-temperature cooking film are as follows: Step S1, obtaining the required raw materials according to the raw material ratio, and adding the raw materials into the corresponding mixing equipment respectively, and stirring them fully to ensure uniform mixing of the raw materials; Step S2, respectively feeding the mixed raw materials into the corresponding extruders of the three-layer co-extrusion casting unit to obtain molten blended raw materials, and respectively passing the obtained molten blended raw materials through a die head composite extrusion technology to closely combine the three layers of molten raw materials together to form a uniform film; Step S3, feeding the film extruded in step S2 into a stretching machine, forming a stretched film with specific strength and toughness through heating and stretching processes, and placing the obtained stretched film into a molding chamber for cooling and molding, and after the stretched film reaches a set temperature state, performing a cooling and molding operation to ensure its dimensional stability and physical properties; Step S4, performing corona treatment on the film to enhance the surface tension of the film and improve its adhesion with ink and glue materials; Step S5, rolling up the stretched film after cooling and shaping, and sending the rolled stretched film into a aging chamber for aging treatment; Step S6: the matured stretched film is cut into pieces to obtain a high-temperature steam-cooked film product that meets product specifications, and a performance test is performed on the obtained high-temperature steam-cooked film product.

[0006] Preferably, the fibrous reinforcement includes one or more of glass fiber, carbon fiber or ceramic fiber, the additive is one or more of a lubricant, a flame retardant, an antioxidant and an anti-ultraviolet agent, and the nylon is one or more of nylon 6, nylon 66, nylon 11 or nylon 12.

[0007] Preferably, in step S1, the stirring speed of the mixing device is 320 r / min to 380 r / min, the stirring temperature is 120° C. to 150° C., and the stirring time is 0.5 h to 1 h.

[0008] Preferably, the extruder in step S2 includes an outer layer extruder, a middle layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 190°C to 230°C, the temperature inside the screw conveying sleeve of the middle layer extruder is 190°C to 215°C, and the temperature inside the screw conveying sleeve of the inner layer extruder is 190°C to 225°C.

[0009] Preferably, in step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 190° C. to 240° C.

[0010] Preferably, the temperature during the stretching process in step S3 is maintained at 160°C to 185°C, the stretching ratio is 1:1.5 to 1:1.7, the temperature in the molding chamber is 140°C, and is reduced at a rate of 0.5°C / min, and the molding time is 1h to 3h.

[0011] Preferably, the cooling temperature is controlled at 15°C to 25°C, and the cooling time is 10min to 30min.

[0012] Preferably, in step S4, the corona value is controlled at 40 to 48 dynes.

[0013] Preferably, in step S5, the aging temperature is 50° C. to 60° C., and the aging time is 4 h to 6 h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention greatly improves the puncture resistance and tensile resistance of the steaming film by adding nylon, fibrous reinforcing agent and styrene-butadiene thermoplastic elastomer. At the same time, when subjected to external force, the steaming film prepared by the present invention can maintain higher ductility and toughness and is not easy to break; 2. The present invention has excellent barrier properties and low water vapor permeability and oxygen permeability. The cooking film of the present invention can effectively prevent external water vapor and oxygen from entering the interior of the package, thereby extending the shelf life and freshness of the items in the package; 3. The present invention improves the dimensional stability by maintaining an appropriate stretching temperature and stretching ratio, and performing a stable cooling and molding process on the obtained stretched film in a molding chamber, and then cooling and shaping. Thus, the dimensional change and mass loss during the high-temperature cooking process can maintain stable shape stability and material integrity; 4. The present invention adopts three-layer co-extrusion casting technology to tightly combine the outer layer, the middle layer and the inner layer, thereby achieving the effect of eliminating the sticky materials between the outer layer, the middle layer and the inner layer, reducing the use of materials with harmful migration, and thus ensuring that the cooking film prepared by the present invention has very little material migrating to food or other packaging materials during high-temperature cooking, thereby improving the safety of the cooking film during use. DETAILED DESCRIPTION

[0015] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] Embodiment 1: An embodiment provided by the present invention: A method for manufacturing a puncture-resistant, low-heat-shrinkage food-grade high-temperature cooking film, comprising an outer layer, a middle layer and an inner layer, wherein the thickness percentage of the outer layer, the middle layer and the inner layer is 30%:15%:55%; The mass percentages of the components of the outer layer are 82.8% of ethoxyethyl acrylate, 14.9% of nylon, 1.9% of fibrous reinforcement and 0.4% of additives, the mass percentages of the components of the middle layer are 76.6% of ethylene-vinyl alcohol copolymer and 23.4% of polyamide, and the mass percentages of the components of the inner layer are 83.6% of ethoxyethyl acrylate, 14.7% of styrene-butadiene thermoplastic elastomer, 1.4% of fibrous reinforcement and 0.3% of additives; The steps for making the puncture-resistant, low heat shrinkage food-grade high-temperature cooking film are as follows: Step S1, obtaining the required raw materials according to the raw material ratio, and adding the raw materials into the corresponding mixing equipment respectively, and stirring them fully to ensure uniform mixing of the raw materials; Step S2, respectively feeding the mixed raw materials into the corresponding extruders of the three-layer co-extrusion casting unit to obtain molten blended raw materials, and respectively passing the obtained molten blended raw materials through a die head composite extrusion technology to closely combine the three layers of molten raw materials together to form a uniform film; Step S3, feeding the film extruded in step S2 into a stretching machine, forming a stretched film with specific strength and toughness through heating and stretching processes, and placing the obtained stretched film into a molding chamber for cooling and molding, and after the stretched film reaches a set temperature state, performing a cooling and molding operation to ensure its dimensional stability and physical properties; Step S4, performing corona treatment on the film to enhance the surface tension of the film and improve its adhesion with ink and glue materials; Step S5, rolling up the stretched film after cooling and shaping, and sending the rolled stretched film into a aging chamber for aging treatment; Step S6, cutting the matured stretched film to obtain a high-temperature steam-cooked film product that meets product specifications, and performing a performance test on the obtained high-temperature steam-cooked film product; The fibrous reinforcing agent includes glass fiber, the additive is a mixed material of a lubricant, an antioxidant and an anti-ultraviolet agent, and the nylon is a mixed material of nylon 6 and nylon 66; In step S1, the stirring speed of the mixing device is 360 r / min, the stirring temperature is 140° C., and the stirring time is 0.7 h; The extruder in step S2 includes an outer layer extruder, an intermediate layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 210° C., the temperature inside the screw conveying sleeve of the intermediate layer extruder is 200° C., and the temperature inside the screw conveying sleeve of the inner layer extruder is 215° C.; In step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 220° C.; The temperature during the stretching process in step S3 is maintained at 170°C, the stretching ratio is 1:1.6, the temperature in the molding chamber is 140°C, and is reduced at a rate of 0.5°C / min, and the molding time is 2h; The cooling temperature was controlled at 20°C and the cooling time was 20 min; In step S4, the corona value is controlled at 44 dynes; In step S5, the aging temperature is 55° C. and the aging time is 5 h.

[0017] Example 2: An example provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the mass percentages of the components of the outer layer are 82.2% of ethoxyethyl acrylate, 15.2% of nylon, 2.3% of fibrous reinforcing agent and 0.3% of additives, the mass percentages of the components of the middle layer are 76.2% of ethylene-vinyl alcohol copolymer and 23.8% of polyamide, and the mass percentages of the components of the inner layer are 83.3% of ethoxyethyl acrylate, 14.8% of styrene-butadiene thermoplastic elastomer, 1.6% of fibrous reinforcing agent and 0.3% of additives; The fibrous reinforcing agent includes a mixed material of glass fiber and carbon fiber, the additives include a lubricant and an anti-ultraviolet agent, and the nylon includes a mixed material of nylon 6 and nylon 11; In step S1, the stirring speed of the mixing device is 320 r / min, the stirring temperature is 150° C., and the stirring time is 1 h; The extruder in step S2 includes an outer layer extruder, a middle layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 230° C., the temperature inside the screw conveying sleeve of the middle layer extruder is 190° C., and the temperature inside the screw conveying sleeve of the inner layer extruder is 225° C.; In step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 240° C.; The temperature during the stretching process in step S3 is maintained at 160° C., the stretching ratio is 1:1.7, the temperature in the molding chamber is 140° C., and is reduced at a rate of 0.5° C. / min, and the molding time is 1 hour; The cooling temperature was controlled at 25°C and the cooling time was 10 min; In step S4, the corona value is controlled at 48 dynes; In step S5, the aging temperature is 50° C. and the aging time is 6 hours.

[0018] Example 3: An example provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the mass percentages of the components of the outer layer are 83.3% of ethoxyethyl acrylate, 15.2% of nylon, 1.2% of fibrous reinforcing agent and 0.3% of additives, the mass percentages of the components of the middle layer are 76.6% of ethylene-vinyl alcohol copolymer and 23.4% of polyamide, and the mass percentages of the components of the inner layer are 83.6% of ethoxyethyl acrylate, 14.6% of styrene-butadiene thermoplastic elastomer, 1.5% of fibrous reinforcing agent and 0.3% of additives; The fibrous reinforcing agent includes one or more ceramic fibers, the additives include a lubricant, a flame retardant, an antioxidant and an anti-ultraviolet agent, and the nylon includes nylon 6; In step S1, the stirring speed of the mixing device is 380 r / min, the stirring temperature is 125° C., and the stirring time is 0.9 h; The extruder in step S2 includes an outer layer extruder, a middle layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 220° C., the temperature inside the screw conveying sleeve of the middle layer extruder is 205° C., and the temperature inside the screw conveying sleeve of the inner layer extruder is 215° C.; In step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 225° C.; The temperature during the stretching process in step S3 is maintained at 175°C, the stretching ratio is 1:1.6, the temperature in the molding chamber is 140°C, and is reduced at a rate of 0.5°C / min, and the molding time is 2.2h; The cooling temperature was controlled at 15°C and the cooling time was 30 min; In step S4, the corona value is controlled at 46 dynes; In step S5, the aging temperature is 57° C. and the aging time is 4.4 h.

[0019] Example 4: An example provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the mass percentages of the components of the outer layer are 83.8% of ethoxyethyl acrylate, 14.6% of nylon, 1.5% of fibrous reinforcing agent and 0.1% of additives, the mass percentages of the components of the middle layer are 76.4% of ethylene-vinyl alcohol copolymer and 23.6% of polyamide, and the mass percentages of the components of the inner layer are 83.8% of ethoxyethyl acrylate, 14.7% of styrene-butadiene thermoplastic elastomer, 1.1% of fibrous reinforcing agent and 0.4% of additives; The fibrous reinforcing agent includes a mixed material of glass fiber, carbon fiber and ceramic fiber, the additive uses a lubricant, and the nylon uses nylon 6 and nylon 12; In step S1, the stirring speed of the mixing device is 380 r / min, the stirring temperature is 145° C., and the stirring time is 1 h; The extruder in step S2 includes an outer layer extruder, an intermediate layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 220° C., the temperature inside the screw conveying sleeve of the intermediate layer extruder is 215° C., and the temperature inside the screw conveying sleeve of the inner layer extruder is 200° C.; In step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 220° C.; The temperature during the stretching process in step S3 is maintained at 174°C, the stretching ratio is 1:1.5, the temperature in the molding chamber is 140°C, and is reduced at a rate of 0.5°C / min, and the molding time is 1.5h; The cooling temperature was controlled at 15°C and the cooling time was 30 min; In step S4, the corona value is controlled at 40 dynes; In step S5, the aging temperature is 60° C. and the aging time is 5 h.

[0020] Example 5: An example provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the mass percentages of the components of the outer layer are 82.8% of ethoxyethyl acrylate, 15.2% of nylon, 1.9% of fibrous reinforcing agent and 0.1% of additives, the mass percentages of the components of the middle layer are 76.8% of ethylene-vinyl alcohol copolymer and 23.2% of polyamide, and the mass percentages of the components of the inner layer are 83.9% of ethoxyethyl acrylate, 14.3% of styrene-butadiene thermoplastic elastomer, 1.1% of fibrous reinforcing agent and 0.7% of additives; The fibrous reinforcing agent includes glass fiber, the additive includes one or more of a lubricant and an anti-ultraviolet agent, and the nylon includes one or more of nylon 12; In step S1, the stirring speed of the mixing device is 380 r / min, the stirring temperature is 135° C., and the stirring time is 0.5 h; The extruder in step S2 includes an outer layer extruder, an intermediate layer extruder and an inner layer extruder, the temperature inside the screw conveying sleeve of the outer layer extruder is 195° C., the temperature inside the screw conveying sleeve of the intermediate layer extruder is 195° C., and the temperature inside the screw conveying sleeve of the inner layer extruder is 195° C.; In step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 200° C.; The temperature during the stretching process in step S3 is maintained at 180°C, the stretching ratio is 1:1.6, the temperature in the molding chamber is 140°C, and is reduced at a rate of 0.5°C / min, and the molding time is 3h; The cooling temperature was controlled at 25°C and the cooling time was 25 min; In step S4, the corona value is controlled at 46 dynes; In step S5, the aging temperature is 56° C. and the aging time is 6 hours.

[0021] Comparative Example 1: An embodiment provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the outer layer adopts a polypropylene resin base material.

[0022] Comparative Example 2: An embodiment provided by the present invention: The specific implementation method is the same as that of Example 1, except that the outer layer uses block copolymer polypropylene, and the middle layer only uses ethylene-vinyl alcohol copolymer.

[0023] Comparative Example 3: An embodiment provided by the present invention: The specific implementation method is the same as that of Example 1, except that: the outer layer uses block copolymer polypropylene, the middle layer uses only ethylene-vinyl alcohol copolymer, and the inner layer uses block copolymer polypropylene and metallocene linear polyethylene containing octene copolymer monomer.

[0024] Performance Test: Test 1: The puncture resistance, tensile strength and elongation at break of the cooking films prepared in Examples 1-5 and Comparative Examples 1-3 were tested. The puncture resistance of the cooking films was tested using a puncture needle, and the tensile strength and elongation at break of the cooking films in both the longitudinal and transverse directions were tested. Test 2: The steam-cooked films prepared in Examples 1-5 and Comparative Examples 1-3 were tested for water vapor permeability and air permeability. The water vapor permeability tester was used to test the film at room temperature and relative humidity of 90%, and the air permeability tester was used to test the film at room temperature and relative humidity of 0%. Test 3: The cooking films prepared in Examples 1-5 and Comparative Examples 1-3 were subjected to high-temperature cooking tests and migration performance tests. The cooking films were placed in a high-temperature and high-humidity environment for cooking at a temperature of 130°C and a relative humidity of 90% for 24 hours. After the cooking was completed, the size change rate, mass loss rate and the content of harmful substances in the cooking film that migrated into the food during the cooking process were obtained. Table 1 Test results of performance test 1

[0025] Furthermore, it can be seen from Table 1 that the cooking film prepared by the present invention greatly improves the puncture resistance and tensile strength of the cooking film by adding nylon and fibrous reinforcement and styrene-butadiene thermoplastic elastomer. At the same time, when subjected to external force, the cooking film prepared by the present invention can maintain higher ductility and toughness and is not easy to break.

[0026] Table 2 Test results of performance test 2

[0027] Furthermore, it can be seen from Table 2 that the cooking film prepared by the present invention can effectively prevent external water vapor and oxygen from entering the interior of the package through excellent barrier properties and low water vapor permeability and oxygen permeability, thereby extending the shelf life and freshness of the items in the package.

[0028] Table 3 Test results of performance test 3

[0029] Furthermore, it can be seen from Table 3 that the cooking film prepared by the present invention can maintain stable shape stability and material integrity in terms of dimensional change and mass loss during high-temperature cooking. At the same time, the cooking film prepared by the present invention has very little material migrating toward food or other packaging materials during high-temperature cooking, thereby improving the safety of the cooking film during use.

[0030] Working principle: by adding nylon and fibrous reinforcement and styrene-butadiene thermoplastic elastomer, the puncture resistance and tensile strength of the cooking film are greatly improved. At the same time, when subjected to external force, the cooking film prepared by the present invention can maintain higher ductility and toughness and is not easy to break. Through the excellent barrier performance setting and low water vapor permeability and oxygen permeability, the cooking film of the present invention can effectively prevent external water vapor and oxygen from entering the interior of the package, thereby extending the shelf life and freshness of the items in the package. During the high-temperature cooking process, the dimensional change and mass loss can maintain stable shape stability and material integrity. At the same time, the cooking film prepared by the present invention has very few substances migrating to food or other packaging materials during high-temperature cooking, thereby improving the safety of the cooking film during use.

[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for manufacturing a puncture-resistant, low-heat-shrinkage food-grade high-temperature cooking film, comprising an outer layer, an intermediate layer and an inner layer, characterized in that: The thickness percentage of the outer layer, the middle layer and the inner layer is 30%:15%:55%; The mass percentages of the components of the outer layer are 82.2% to 83.8% of ethoxyethyl acrylate, 14.5% to 15.2% of nylon, 1% to 2.7% of fibrous reinforcing agent, and 0.1% to 0.5% of additives; the mass percentages of the components of the middle layer are 76.2% to 76.8% of ethylene-vinyl alcohol copolymer and 23.2% to 23.8% of polyamide; the mass percentages of the components of the inner layer are 83.3% to 83.9% of ethoxyethyl acrylate, 14.3% to 14.8% of styrene-butadiene thermoplastic elastomer, 1.1% to 1.6% of fibrous reinforcing agent, and 0.1% to 0.7% of additives; The steps for making the puncture-resistant, low heat shrinkage food-grade high-temperature cooking film are as follows: Step S1, obtaining the required raw materials according to the raw material ratio, and adding the raw materials into the corresponding mixing equipment respectively, and stirring them fully to ensure uniform mixing of the raw materials; Step S2, respectively feeding the mixed raw materials into the corresponding extruders of the three-layer co-extrusion casting unit to obtain molten blended raw materials, and respectively passing the obtained molten blended raw materials through a die head composite extrusion technology to closely combine the three layers of molten raw materials together to form a uniform film; Step S3, feeding the film extruded in step S2 into a stretching machine, forming a stretched film with specific strength and toughness through heating and stretching processes, and placing the obtained stretched film into a molding chamber for cooling and molding, and after the stretched film reaches a set temperature state, performing a cooling and molding operation to ensure its dimensional stability and physical properties; Step S4, performing corona treatment on the film to enhance the surface tension of the film and improve its adhesion with ink and glue materials; Step S5, rolling up the stretched film after cooling and shaping, and sending the rolled stretched film into a aging chamber for aging treatment; Step S6: the matured stretched film is cut into pieces to obtain a high-temperature steam-cooked film product that meets product specifications, and a performance test is performed on the obtained high-temperature steam-cooked film product.

2. The method for producing a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: The fibrous reinforcing agent includes one or more of glass fiber, carbon fiber or ceramic fiber, the additive includes one or more of lubricant, flame retardant, antioxidant and UV inhibitor, and the nylon includes one or more of nylon 6, nylon 66, nylon 11 or nylon 12.

3. The method for producing a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: In the step S1, the stirring speed of the mixing device is 320 r / min to 380 r / min, the stirring temperature is 120° C. to 150° C., and the stirring time is 0.5 h to 1 h.

4. The method for producing a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: The extruder in step S2 includes an outer layer extruder, a middle layer extruder and an inner layer extruder. The temperature inside the screw conveying sleeve of the outer layer extruder is 190°C to 230°C, the temperature inside the screw conveying sleeve of the middle layer extruder is 190°C to 215°C, and the temperature inside the screw conveying sleeve of the inner layer extruder is 190°C to 225°C.

5. The method for making a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: In the step S2, the die flow channel temperatures of the outer layer extruder, the middle layer extruder and the inner layer extruder are all 190° C. to 240° C.

6. The method for making a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: The temperature during the stretching process in step S3 is maintained at 160° C. to 185° C., the stretching ratio is 1:1.5 to 1:1.7, the temperature in the molding chamber is 140° C., and is reduced at a rate of 0.5° C. / min, and the molding time is 1 h to 3 h.

7. The method for making a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: The cooling temperature is controlled at 15°C to 25°C, and the cooling time is 10min to 30min.

8. The method for making a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: In step S4, the corona value is controlled at 40 to 48 dynes.

9. The method for producing a puncture-resistant, low heat shrinkage food-grade high-temperature cooking film according to claim 1, characterized in that: In step S5, the aging temperature is 50° C. to 60° C., and the aging time is 4 h to 6 h.

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