A hot-melt adhesive for food packaging, a method for preparing the same, and an electromagnetic induction sealing method

Abstract

This application belongs to the field of adhesive technology, and relates to a hot melt adhesive for food packaging, its preparation method, and an electromagnetic induction sealing method. The hot melt adhesive for food packaging includes petroleum resin, ethylene-vinyl acetate copolymer, polyisobutylene, and composite wax, and the composite wax includes a combination of microcrystalline wax with a dropping melting point ≥85℃, polyethylene wax, oxidized polyethylene wax, and Fischer-Tropsch wax. By selecting the above-mentioned four specific wax materials for composite, and combining them with specific resin components and toughening and tackifying components, the resulting hot melt adhesive for food packaging has low kinematic viscosity, high heat resistance, and excellent film-forming properties. It has specific interfacial bonding force with aluminum foil, does not crack or fall off, and has strong adhesive properties. It can be melted and cooled under electromagnetic induction conditions and firmly bonded together, ensuring that the sealed contents do not leak or become airtight, while also fully complying with the safety performance requirements of GB 4806 series.

Description

Technical Field

[0001] This application belongs to the field of adhesive technology, and relates to a hot melt adhesive for food packaging, its preparation method, and an electromagnetic induction sealing method. Background Technology

[0002] Food packaging adhesives, as core functional materials ensuring the strength of packaging composites and maintaining food safety, are widely used in various packaging forms such as paper boxes, plastic bags, composite films, and electromagnetic induction sealing gaskets. Their role is not only to ensure the integrity of the packaging structure and prevent food leakage and external contamination, but also to play a crucial role in extending shelf life and enhancing the consumer experience. The technical mechanism of these adhesives is mainly based on polymer chemistry and interface science. They are typically composed of a resin matrix, solvent, curing agent, and various additives. Through physical entanglement or chemical cross-linking, they form a high-strength adhesive layer on the substrate surface, requiring excellent initial tack, holding power, and peel strength to meet the process requirements of automated packaging production lines.

[0003] In existing technologies, polyurethane, water-based emulsions, hot melt adhesives, and pressure-sensitive adhesives constitute the mainstream in the market, and their formulation systems exhibit highly differentiated characteristics depending on the food contents, the temperature and humidity of the application environment, and the properties of the substrate. However, in specific application scenarios involving electromagnetic induction sealing, especially in the food packaging field, existing adhesive systems have revealed many insurmountable technical defects, severely restricting packaging safety and production efficiency. First, the temperature resistance is insufficient. Traditional food packaging adhesives generally have low melting points (usually below 60°C), making them prone to thermal softening in high-temperature storage or transportation environments during summer. This can lead to interlayer blocking in prefabricated gaskets or, after packaging, seal failure and leakage risks due to adhesive layer creep.

[0004] Secondly, it has poor processability. Existing adhesives generally suffer from difficulties in viscosity control, making it difficult to prepare ultra-thin, uniform adhesive films with a thickness ranging from 1 to 5 filaments (0.01 to 0.05 mm) through coating processes. This defect directly limits its application in high-end precision sealing gaskets; excessively thick adhesive layers not only waste raw materials but also affect the conduction efficiency of electromagnetic induction heat.

[0005] Secondly, there is an imbalance in the interfacial bonding force between the aluminum foil substrate and the substrate. The adhesive is easily peeled off from the aluminum foil surface after being heated and is instead absorbed by the backing material, resulting in a lack of effective adhesive medium between the aluminum foil and the container opening, causing a "false seal".

[0006] Furthermore, production flow issues are also significant. When prefabricated gaskets are stacked and stored, improper adhesive surface energy or anti-sticking treatment can easily lead to back-side adhesion, making it difficult for robotic arms on automated production lines to accurately pick up individual gaskets using vacuum suction. Simultaneously, when die-cutting large-format rolls into gaskets of specific shapes, existing adhesives are prone to stringing or adhesion at the edges, severely impacting die-cutting accuracy and production efficiency.

[0007] Finally, compliance and sensory quality standards are not met. Some traditional adhesives release odors during production or use, affecting food flavor. More importantly, with the formal implementation of GB 4806.15-2024 "National Food Safety Standard for Adhesives for Food Contact Materials and Products," stricter limits have been imposed on the migration of aromatic amines, heavy metals, and volatile organic compounds (VOCs) in adhesives. Many existing general-purpose food packaging adhesives cannot fully meet the new national standard's regulations regarding additive use and specific migration limits, posing potential food safety compliance risks.

[0008] Therefore, there is an urgent need to develop a hot melt adhesive for food packaging that combines low viscosity, high heat resistance, excellent film-forming properties, specific interfacial bonding to aluminum foil, good anti-blocking performance, and fully complies with the requirements of the GB 4806 series standards. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the purpose of this application is to provide a hot melt adhesive for food packaging, its preparation method, and an electromagnetic induction sealing method. The hot melt adhesive for food packaging has low viscosity, high heat resistance, and excellent film-forming properties. It also has a specific interfacial bonding force with aluminum foil, and can be firmly bonded together after melting and cooling under electromagnetic induction conditions, ensuring that the sealed object is leak-proof and airtight, and fully complies with the safety performance requirements of GB 4806.15-2024.

[0010] To achieve this objective, the present application adopts the following technical solution: In a first aspect, this application provides a hot melt adhesive for food packaging, which comprises the following components by weight: 1-10 parts by weight of petroleum resin; 5-30 parts by weight of ethylene-vinyl acetate copolymer; 2-10 parts by weight of polyisobutylene; 20-150 parts by weight of compound wax; The composite wax comprises a combination of microcrystalline wax with a melting point ≥85℃, polyethylene wax, oxidized polyethylene wax, and Fischer-Tropsch wax.

[0011] The hot melt adhesive for food packaging provided in this application comprises specific weight parts of petroleum resin, ethylene-vinyl acetate copolymer, polyisobutylene, and composite wax, and specifies that the composite wax includes a combination of microcrystalline wax with a dropping melting point ≥85℃, polyethylene wax, oxidized polyethylene wax, and Fischer-Tropsch wax; by selecting the above-mentioned four specific wax materials for compounding, and combining them with resin components and toughening and tackifying components, the resulting hot melt adhesive for food packaging has the following advantages: ① Low kinematic viscosity, easy to apply, and capable of preparing films; ② Excellent high-temperature resistance, able to withstand high temperatures, and does not soften during summer storage. ① It has good adhesion; ② It has good film-forming properties and high adhesion, with specific interfacial bonding force to aluminum foil. It has good spreadability and adhesion on aluminum foil, does not crack or fall off, and has strong adhesive properties. After melting and cooling under electromagnetic induction conditions, it firmly adheres to the same surface, ensuring that the sealed object does not leak or become airtight; ③ It has high elastic modulus below the softening point temperature. When cut into a certain shape according to packaging requirements, the edges are not easy to stick together. It has excellent compressive strength when stacked and has an anti-sticking effect. It can be separated individually when mechanical tentacles grasp / pick up, which is convenient for construction; ④ It has high safety performance and meets the relevant requirements of GB 4806.15-2024 "Adhesives for Food Contact Materials and Products".

[0012] In this application, the content of the petroleum resin can be 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight, etc.

[0013] The content of the ethylene-vinyl acetate copolymer can be 5 parts by weight, 10 parts by weight, 15 parts by weight, 20 parts by weight, 25 parts by weight, or 30 parts by weight, etc.

[0014] The content of polyisobutylene can be 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight, etc.

[0015] The content of the composite wax can be 20 parts by weight, 40 parts by weight, 60 parts by weight, 80 parts by weight, 100 parts by weight, 120 parts by weight, 140 parts by weight, or 150 parts by weight, etc.

[0016] In some specific embodiments, the petroleum resin includes any one or a combination of at least two of C5 aliphatic petroleum resin, C9 aromatic petroleum resin, C5 / C9 copolymer petroleum resin, DCPD alicyclic petroleum resin, or hydrogenated modified petroleum resin, preferably C9 hydrogenated petroleum resin and / or DCPD alicyclic petroleum resin.

[0017] In some specific embodiments, the mass percentage of vinyl acetate structure in the ethylene-vinyl acetate copolymer is 10-40%, such as 10%, 15%, 20%, 25%, 30%, 35% or 40%, preferably 28-33%.

[0018] In some specific embodiments, the melt index of the ethylene-vinyl acetate copolymer at 190°C and 2.16 kg is 150~800 g / 10min, such as 150 g / 10min, 200 g / 10min, 250 g / 10min, 300 g / 10min, 400 g / 10min, 500 g / 10min, 600 g / 10min, 700 g / 10min or 800 g / 10min, etc., preferably 150~420 g / 10min.

[0019] In some specific embodiments, the number average molecular weight of the polyisobutylene is 10,000 to 100,000, such as 20,000, 40,000, 50,000, 60,000, 65,000, 70,000, 75,000, 80,000, 90,000, 95,000, or 100,000.

[0020] In some specific embodiments, the mass ratio of the microcrystalline wax, polyethylene wax, oxidized polyethylene wax and Fischer-Tropsch wax is (5~30):(5~30):(5~30):(5~40); The mass ratio of the microcrystalline wax to the polyethylene wax can be 5:5, 5:7, 5:9, 5:11, 5:13, 5:15, 5:17, 5:19, 5:21, 5:23, 5:25, 5:27, 5:30, 7:5, 9:5, 11:5, 13:5, 15:5, 17:5, 19:5, 21:5, 23:5, 25:5, 27:5, or 30:5, etc.; the mass ratio of the microcrystalline wax to the oxidized polyethylene wax can be 5:5, 5:7, 5:9, 5:11, 5:13, 5:15, 5:17, 5:19, 5:21, 5:23, 5:25, 5: The mass ratio of the microcrystalline wax to the Fischer-Tropsch wax can be 5:5, 5:30, 7:5, 9:5, 11:5, 13:5, 15:5, 17:5, 19:5, 21:5, 23:5, 25:5, 27:5, or 30:5, etc.;

[0021] In some specific embodiments, the number average molecular weight of the polyethylene wax is 1000~8000, such as 1000, 2000, 3000, 4000, 5000, 6000, 7000 or 8000, preferably 3000~5000.

[0022] In some specific embodiments, the density of the oxidized polyethylene wax is 0.91~0.94 g / cm³. 3 For example, 0.915 g / cm³ 3 0.92 g / cm 3 0.925 g / cm 3 0.93 g / cm 3 Or 0.935 g / cm 3 wait.

[0023] In some specific embodiments, the number average molecular weight of the oxidized polyethylene wax is 500 to 5000, such as 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500 or 5000, preferably 2000 to 3000.

[0024] In some specific embodiments, the acid value of the oxidized polyethylene wax is ≤20 mgKOH / g, such as 20 mgKOH / g, 18 mgKOH / g, 16 mgKOH / g, 14 mgKOH / g, 12 mgKOH / g, 10 mgKOH / g, 8 mgKOH / g, or 6 mgKOH / g, etc.

[0025] In some specific embodiments, the Fischer-Tropsch wax has a melting point ≥80°C, such as 85°C, 90°C, 92°C, 94°C, 96°C, 98°C, or 100°C.

[0026] In some specific embodiments, the hot melt adhesive for food packaging further includes any one or a combination of at least two of antioxidants, internal lubricants, or external lubricants.

[0027] In some specific embodiments, the antioxidant content in the hot melt adhesive for food packaging is 0.5 to 1 part by weight, such as 0.5 parts by weight, 0.6 parts by weight, 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, or 1 part by weight.

[0028] In some specific embodiments, the antioxidant includes hindered phenolic antioxidants and / or phosphite antioxidants.

[0029] In some specific embodiments, the content of the internal lubricant in the hot melt adhesive for food packaging is 0.5 to 10 parts by weight, such as 0.5 parts by weight, 1 part by weight, 2 parts by weight, 4 parts by weight, 6 parts by weight, 8 parts by weight, or 10 parts by weight.

[0030] In some specific embodiments, the internal lubricant includes any one or a combination of at least two of fatty acid ester internal lubricants, fatty acid amide internal lubricants, polyethylene wax, or polypropylene wax, and is more preferably a fatty acid amide internal lubricant.

[0031] In some specific embodiments, the fatty amide internal lubricant includes ethylene bis-stearamide.

[0032] In some specific embodiments, the content of external lubricant in the hot melt adhesive for food packaging is 0.5 to 10 parts by weight, such as 0.5 parts by weight, 1 part by weight, 2 parts by weight, 4 parts by weight, 6 parts by weight, 8 parts by weight, or 10 parts by weight.

[0033] In some specific embodiments, the external lubricant includes any one or a combination of at least two of fatty acid amide external lubricants, stearic acid and its metal soaps, Fischer-Tropsch wax or modified organosilicon, and is more preferably a fatty acid amide external lubricant. In some specific embodiments, the fatty acid amide external lubricant includes oleamide.

[0034] Secondly, this application provides a method for preparing a hot melt adhesive for food packaging as described in the first aspect, the method comprising the following steps: (1) Microcrystalline wax, polyethylene wax, oxidized polyethylene wax and Fischer-Tropsch wax are mixed to obtain a composite wax; (2) The composite wax obtained in step (1), the ethylene-vinyl acetate copolymer and the polyisobutylene are mixed to obtain a mixture; (3) The mixture obtained in step (2), petroleum resin, optional antioxidant, optional internal lubricant and optional external lubricant are mixed and cast to obtain the hot melt adhesive for food packaging.

[0035] In some specific embodiments, the mixing temperature in step (1) is 110~120℃, such as 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃ or 120℃.

[0036] In some specific embodiments, the mixing time in step (1) is 1 to 1.5 h, such as 1.05 h, 1.1 h, 1.15 h, 1.2 h, 1.25 h, 1.3 h, 1.35 h, 1.4 h or 1.45 h.

[0037] In some specific embodiments, the mixing temperature in step (2) is 130~135℃, such as 130℃, 131℃, 132℃, 133℃, 134℃ or 135℃.

[0038] In some specific embodiments, the mixing time in step (2) is 0.5 to 1 h, for example, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h.

[0039] In some specific embodiments, the mixing temperature in step (3) is 110~130℃, such as 110℃, 112℃, 114℃, 116℃, 118℃, 120℃, 122℃, 124℃, 126℃, 128℃ or 130℃.

[0040] In some specific embodiments, the mixing time in step (3) is 1 to 1.5 min, for example 1.05 min, 1.1 min, 1.15 min, 1.2 min, 1.25 min, 1.3 min, 1.35 min, 1.4 min or 1.45 min, etc.

[0041] Thirdly, this application provides an electromagnetic induction sealing method using the hot melt adhesive for food packaging as described in the first aspect. The electromagnetic induction sealing method includes: applying the hot melt adhesive for food packaging as described in the first aspect to an aluminum foil food packaging material, adding the packaged item and folding it, heating the aluminum foil through electromagnetic induction, and at the same time melting the adhesive to achieve self-adhesion, thereby completing the electromagnetic induction sealing.

[0042] In some specific embodiments, the coating thickness is 0.01~0.05 mm, for example 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm or 0.05 mm.

[0043] Compared with the prior art, this application has the following advantages: The hot melt adhesive for food packaging provided in this application has low kinematic viscosity, is easy to apply, can effectively prepare films, and has good spreadability and adhesion on aluminum foil. After electromagnetic induction, the hot melt adhesive will not detach from the aluminum foil and has strong adhesive properties, firmly adhering together to ensure that the sealed contents are leak-proof and airtight. The hot melt adhesive for food packaging also has excellent die-cutting performance. Below the softening point temperature, its elastic modulus is higher than its energy dissipation modulus. When cut into a certain shape according to packaging requirements, the edges are not easy to stick together and can be separated individually during mechanical gripping / pickup operations, facilitating construction. It also meets the relevant requirements of GB 4806.15-2024 "Adhesives for Food Contact Materials and Articles". Detailed Implementation

[0044] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0045] The detailed information of some of the raw materials involved in the following specific implementation method is shown below: (1) Petroleum resin C9 hydrogenated petroleum resin: purchased from Henghe Materials Technology Co., Ltd., grade HF-100.

[0046] (2) Ethylene-vinyl acetate copolymer EVA-1: VA content is 28%, melt index is 150 g / 10min (190℃ / 2.16 kg), purchased from Dow Chemical, brand name Elvax® 150; EVA-2: VA content is 33%, melt index is 400 g / 10min (190℃ / 2.16 kg), purchased from Arkema, grade EVA33-400.

[0047] (3) Polyisobutylene Polyisobutylene: weight average molecular weight 53000 g / mol, purchased from BASF, grade B10N.

[0048] (4) Composite wax Microcrystalline wax: melting point >85℃, purchased from Jingmen Weijia Industrial Co., Ltd., grade 85# microcrystalline wax; PE wax: melting point 103℃, number average molecular weight 4000, purchased from Waxon, grade JC205; OPE wax-1: melting point 105℃, number average molecular weight 2500, acid value 17 mgKOH / g, purchased from Westlake, brand name EPOLENE® E-10; OPE wax-2: melting point 104℃, number average molecular weight 3500, acid value 17 mgKOH / g, purchased from Westlake, brand name EPOLENE® E-14; OPE wax-3: melting point 114℃, number average molecular weight 5000, acid value 17 mgKOH / g, purchased from Westlake, brand name EPOLENE® E-20; Fischer-Tropsch wax: melting point 80℃, purchased from Inner Mongolia Yitai Group, grade YT80.

[0049] (5) Functional additives Hindered phenolic antioxidants: Antioxidant 1010; Phosphite antioxidants: Antioxidant 626.

[0050] External lubricant: oleic acid amide; Internal lubricant: Erucamide.

[0051] Examples 1-6 and Comparative Examples 1-5 Examples 1-6 and Comparative Examples 1-5 each provide a hot melt adhesive for food packaging. The components and their amounts are shown in Table 1. In Table 1, the amount of each component is in "parts by weight". Table 1 The preparation methods of the hot melt adhesives for food packaging provided in Examples 1-6 and Comparative Examples 1-5 include the following steps: (1) Under nitrogen gas protection, microcrystalline wax, polyethylene wax, oxidized polyethylene wax and Fischer-Tropsch wax are heated to 20°C to melt and stirred evenly to obtain composite wax liquid; (2) Under stirring, polyisobutylene is slowly added to the composite wax liquid obtained in step (1), the temperature is raised to 130°C, and strong mechanical stirring is maintained for 0.5 h until it is completely melted and dispersed evenly to obtain a mixture; (3) After the temperature drops to 120°C, the petroleum resin and functional additives obtained in step (2) are added to the mixture obtained in step (2), stirred until completely dispersed, and then cast to obtain the hot melt adhesive material.

[0052] Performance testing: (1) Kinematic viscosity at 120℃: The test was conducted according to the method provided in GB / T 265 "Determination of Kinematic Viscosity and Calculation of Dynamic Viscosity of Petroleum Products". (2) Softening point; the test shall be conducted in accordance with the method provided in GB / T 4507 "Determination of softening point of bitumen (ring and ball method)".

[0053] (3) Average load: The average load of the 90° peel test at 25° is measured by referring to Appendix B of GB / T 2792 "Test Method for Peel Strength of Adhesive Tape".

[0054] The hot melt adhesives for food packaging provided in Examples 1-6 and Comparative Examples 1-5 were tested according to the above test methods. The test results are shown in Table 2. Table 2 According to the data in Table 2: The hot melt adhesives for food packaging provided in Examples 1-6 have a kinematic viscosity of no more than 1054.8 mm at 120°C. 2 / s, softening point not lower than 103.2℃, average load in the 90° peel range at 25℃ not lower than 6.5 N, and has low kinematic viscosity, high heat resistance and excellent adhesion properties.

[0055] Compared with Example 1, the average load of the hot melt adhesives for food packaging provided by Comparative Examples 1 to 5 in the 90° peel range at 25°C is lower, and Comparative Examples 1 and 4 have higher kinematic viscosity. They cannot simultaneously possess low kinematic viscosity, high heat resistance and excellent adhesion performance.

[0056] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A hot melt adhesive for food packaging, characterized in that, The hot melt adhesive for food packaging comprises the following components by weight: 1-10 parts by weight of petroleum resin; 5-30 parts by weight of ethylene-vinyl acetate copolymer; 2-10 parts by weight of polyisobutylene; 20-150 parts by weight of compound wax; The composite wax comprises a combination of microcrystalline wax with a dropping melting point ≥85℃, polyethylene wax, oxidized polyethylene wax, and Fischer-Tropsch wax.

2. The hot melt adhesive for food packaging according to claim 1, characterized in that, The petroleum resin includes any one or a combination of at least two of C5 aliphatic petroleum resin, C9 aromatic petroleum resin, C5 / C9 copolymer petroleum resin, DCPD alicyclic petroleum resin or hydrogenated modified petroleum resin, preferably C9 hydrogenated petroleum resin and / or DCPD alicyclic petroleum resin. And / or, the mass percentage of vinyl acetate structure in the ethylene-vinyl acetate copolymer is 10-40%, preferably 28-33%; And / or, the melt index of the ethylene-vinyl acetate copolymer at 190°C and 2.16 kg is 150~800 g / 10min, preferably 150~420 g / 10min.

3. The hot melt adhesive for food packaging according to claim 1 or 2, characterized in that, The number-average molecular weight of the polyisobutylene is 10,000 to 100,000.

4. The hot melt adhesive for food packaging according to any one of claims 1 to 3, characterized in that, The mass ratio of the microcrystalline wax, polyethylene wax, oxidized polyethylene wax and Fischer-Tropsch wax is (5~30):(5~30):(5~30):(5~40); And / or, the number average molecular weight of the polyethylene wax is 1000~8000, preferably 3000~5000; And / or, the density of the oxidized polyethylene wax is 0.91~0.94 g / cm³. 3 ; And / or, the number average molecular weight of the oxidized polyethylene wax is 500-5000, preferably 2000-3000; And / or, the acid value of the oxidized polyethylene wax is ≤20 mgKOH / g; And / or, the melting point of the Fischer-Tropsch wax is ≥80°C.

5. The hot melt adhesive for food packaging according to any one of claims 1 to 4, characterized in that, The hot melt adhesive for food packaging also includes any one or a combination of at least two of antioxidants, internal lubricants, or external lubricants. Preferably, the antioxidant content in the hot melt adhesive for food packaging is 0.5 to 1 part by weight; Preferably, the antioxidant includes hindered phenolic antioxidants and / or phosphite antioxidants; Preferably, the content of the internal lubricant in the hot melt adhesive for food packaging is 0.5 to 10 parts by weight; Preferably, the internal lubricant includes any one or a combination of at least two of fatty acid ester internal lubricants, fatty acid amide internal lubricants, polyethylene wax or polypropylene wax, and more preferably a fatty acid amide internal lubricant. Preferably, the fatty amide internal lubricant includes ethylene bis-stearamide; Preferably, the content of external lubricant in the hot melt adhesive for food packaging is 0.5 to 10 parts by weight; Preferably, the external lubricant includes any one or a combination of at least two of fatty acid amide external lubricants, stearic acid and its metal soaps, Fischer-Tropsch wax, or modified organosilicon, and more preferably, a fatty acid amide external lubricant. Preferably, the fatty acid amide external lubricant includes oleamide.

6. A method for preparing a hot melt adhesive for food packaging as described in any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: (1) Microcrystalline wax, polyethylene wax, oxidized polyethylene wax and Fischer-Tropsch wax are mixed to obtain a composite wax; (2) The composite wax obtained in step (1), the ethylene-vinyl acetate copolymer and the polyisobutylene are mixed to obtain a mixture; (3) The mixture obtained in step (2), petroleum resin, optional antioxidant, optional internal lubricant and optional external lubricant are mixed and cast to obtain the hot melt adhesive for food packaging.

7. The preparation method according to claim 6, characterized in that, The mixing temperature in step (1) is 110~120℃ and the time is 1~1.5 h.

8. The preparation method according to claim 6 or 7, characterized in that, The mixing temperature in step (2) is 130~135℃ and the time is 0.5~1 h.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The mixing temperature in step (3) is 110~130℃ and the time is 1~1.5 min.

10. An electromagnetic induction sealing method using a hot melt adhesive for food packaging as described in any one of claims 1 to 5, characterized in that, The electromagnetic induction sealing method includes: coating the hot melt adhesive for food packaging as described in any one of claims 1 to 5 onto the aluminum foil of the food packaging material, adding the packaged item and folding it, heating the aluminum foil through electromagnetic induction, and at the same time melting the adhesive to achieve self-adhesion, thereby completing the electromagnetic induction sealing.

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