Hot-melt composite film as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to a hot-melt composite film as well as a preparation method and application thereof. The film inner layer is made of low-melting-point copolyester with the melting point of 160-200 DEG C; the core layer is made of medium-melting-point copolyester with the melting point of 220-230 DEG C; and the outer layer is made of high-melting-point copolyester with the melting point of 270-290 DEG C. According to the invention, the raw materials of the inner layer, the core layer and the outer layer are subjected to solid-phase tackifying and then are fused and plasticized by using a double-screw extruder to enter a distributor and a die head, and the three layers of melts are instantly laminated at the die lip position of the hanger-shaped die head; and the hot-melt composite film is obtained through the procedures of cold roller cooling, hot air preheating, synchronous biaxial stretching, heat setting, cold air cooling and the like, and the hot-melt composite film has the characteristics of high adhesiveness with aluminum materials, acid resistance, alkali resistance, salt resistance and steaming and boiling resistance and has wide application prospects.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a hot-melt composite film, its preparation method and application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In aluminum container applications, the chemical properties of aluminum determine its reactivity with acids, alkalis, and other substances. Therefore, the material compatibility of the inner wall of the aluminum cup, as the interface directly in contact with the contents, significantly impacts safety. Common everyday fruit juices (such as orange, lemon, apple, and tomato juice) and vinegar and vinegar-containing condiments (such as salad dressing and kimchi juice), if in prolonged contact with the inner wall of an aluminum cup, can trigger electrochemical corrosion, leading to localized pitting, surface roughness, or blackening, accompanied by the dissolution of aluminum ions. Studies have shown that excessive aluminum intake may pose a potential health risk to the nervous system. Furthermore, alkaline media (such as strongly alkaline detergents) can also corrode the aluminum surface under prolonged immersion conditions, promoting the migration of aluminum ions into the solution. High-salt liquids (such as salt water or brine) also exacerbate the corrosion process on the aluminum surface, promoting oxide film formation and potentially inducing pitting and other localized corrosion forms, affecting the container's lifespan and safety.

[0004] To address the issue of the contents coming into contact with aluminum, most aluminum cups on the market have a protective coating applied to their inner walls. Common protective coatings include epoxy resin and ceramic coatings. However, epoxy resin and ceramic coatings have the following problems: (1) Epoxy resin coatings emit a large amount of VOCs during the application process to aluminum cups; (2) Ceramic coatings are very prone to cracking under the scratches of sharp metal. Summary of the Invention

[0005] In view of this, the present invention provides a hot-melt composite film, its preparation method, and its application. The hot-melt composite film provided by the present invention has a three-layer structure and is a hot-melt composite film with strong adhesion to aluminum, acid resistance, alkali resistance, salt resistance, and boiling resistance. The preparation method is simple and easy to process and shape, and it has broad application prospects.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a hot-melt composite film, wherein the hot-melt composite film comprises, from the inside out, an inner layer, a core layer, and an outer layer; the inner layer is made of a low-melting-point copolyester with a melting point of 160-200 °C; the core layer is made of a medium-melting-point copolyester with a melting point of 220-230 °C; and the outer layer is made of a high-melting-point copolyester with a melting point of 270-290 °C.

[0007] Furthermore, the low-melting-point copolyester is prepared from terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO); ​​its intrinsic viscosity is 0.80-1.2 dl / g; using this low-melting-point copolyester as the inner layer can achieve high thermal adhesion properties with aluminum materials.

[0008] Furthermore, the medium-melting-point copolyester is prepared from terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO); ​​its intrinsic viscosity is 0.80-1.5 dl / g; using this medium-melting-point copolyester as the core layer can achieve resistance to deep drawing, boiling, and barrier properties during the stamping process of aluminum cups.

[0009] Furthermore, the high-melting-point copolyester is prepared from terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate (CaCO3); its intrinsic viscosity is 0.80-1.2 dl / g; using this high-melting-point copolyester as the outer layer can achieve acid resistance, alkali resistance, and salt resistance after hot-melt bonding with an aluminum cup.

[0010] Furthermore, the thickness of the hot-melt composite film is 10~20 μm.

[0011] Furthermore, the thickness ratio of the three layers of the hot-melt composite film is inner layer: core layer: outer layer = 15~30: 60~80: 5~15.

[0012] Furthermore, the hot-melt composite film does not turn white during steam cooking at 121 °C for 60 min.

[0013] Furthermore, the hot-melt composite film did not change color after 72 hours in a 10% NaOH alkaline solution at room temperature.

[0014] Furthermore, the hot-melt composite film did not change color after 72 hours in a 2% acetic acid and citric acid solution at room temperature.

[0015] Furthermore, the hot-melt composite film did not change color after 72 hours in a 10% sodium chloride solution at room temperature.

[0016] Furthermore, the CO2 barrier properties of the hot-melt composite film (@23 ℃, 65% RH) are less than 10 cm. 3 ·mm / (m) 2 • 24h·bar); O2 barrier properties of the hot-melt composite film (@23 ℃, 65% RH) are less than 1.5 cm. 3 ·mm / (m) 2 The H2O barrier properties of the hot-melt composite film (@38 ℃, 90% RH) are less than 0.6 g·mm / (m·bar). 2 •24 h).

[0017] In a second aspect, the present invention provides a method for preparing the hot-melt composite film described in the first aspect, comprising the following steps: (1) Low melting point copolyester with a melting point of 160-200 ℃, medium melting point copolyester with a melting point of 220-230 ℃, and high melting point copolyester with a melting point of 270-290 ℃ are melted and plasticized by an extruder to become melts, which are then filtered and fed into the adapter to reach the inner layer, core layer and outer layer of the die head respectively. (2) The inner layer, core layer and outer layer melts are superimposed and flow out through the die head and then cooled to form a primary casting sheet; (3) The primary casting is preheated in air, biaxially stretched, heat-set and cooled to form a hot melt composite film.

[0018] Furthermore, in step (1), a disc filter with a diameter of 20-40 μm is used for filtration.

[0019] Furthermore, in step (1), the adapter is a three-layer adapter.

[0020] Furthermore, in step (1), the mold head is a three-layer "clothes hanger" mold head.

[0021] Furthermore, in step (2), the inner layer, core layer and outer layer melts overlap and flow out at the die lip position of the die head.

[0022] Further, in step (2), a rapid cooling roller is used to cool the device under the force field of the electrostatic adsorption device. The voltage of the electrostatic adsorption device is 10~20 kV; the current of the electrostatic adsorption device is 3~10 mA; and the temperature after cooling is 10~40 ℃.

[0023] Furthermore, in step (2), the thickness of the primary casting is 100~200 μm.

[0024] Furthermore, in step (3), the thickness of the hot melt composite film is 10~20 μm.

[0025] Further, in step (3), the primary casting is preheated at 80~120 ℃, biaxially stretched at 100~130 ℃, heat-set at 150~230 ℃, and cooled at 40~100 ℃ to form a 10~20 μm hot melt composite film.

[0026] Furthermore, in step (3), the biaxial stretching is synchronous stretching; the biaxial stretching ratio is 1.5 to 3.0 times in the longitudinal direction and 1.5 to 3.0 times in the transverse direction; the medium for biaxial stretching is hot air; the wind speed of the hot air for biaxial stretching is 10 to 30 m / s.

[0027] Furthermore, the thickness ratio of the three layers of the hot-melt composite film is inner layer: core layer: outer layer = 15~30: 60~80: 5~15.

[0028] Furthermore, the specific operation of step (1) is as follows: Low-melting-point copolyester chips with a melting point of 160-200 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the inner layer of the three-layer adapter and finally reaches the inner layer of the three-layer "coat hanger" die head. Medium-melting-point copolyester chips with a melting point of 220-230 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the middle layer of the three-layer adapter and finally reaches the core layer of the three-layer "coat hanger" die. High-melting-point copolyester chips with a melting point of 270-290 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0029] Furthermore, the preparation method of low-melting-point copolyesters with a melting point of 160-200 ℃ is as follows: A low-melting-point copolyester with a melting point of 160-200℃ is obtained by esterification and polycondensation of refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) in the presence of catalyst and stabilizer.

[0030] Furthermore, the weight ratio of terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) is 45~80:5~25:5~20:5~10:5~10.

[0031] Furthermore, the esterification reaction temperature is 230~260 ℃, and the time is 2~5 h; the polycondensation reaction temperature is 270~290 ℃, and the vacuum degree is 10~100 Pa.

[0032] Furthermore, the vacuum degree of vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h.

[0033] Furthermore, the preparation method of the medium-melting-point copolyester with a melting point of 220-230 ℃ is as follows: A medium-melting-point copolyester with a melting point of 220-230℃ is obtained by esterification and polycondensation of refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) in the presence of catalyst and stabilizer.

[0034] Furthermore, the weight ratio of terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) is 30~80:5~25:10~60:4~10:1~5.

[0035] Furthermore, the esterification reaction temperature is 230~260 ℃, and the time is 1~3 h; the polycondensation reaction temperature is 260~290 ℃, and the vacuum degree is 20~100 Pa.

[0036] Furthermore, the vacuum degree of vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h.

[0037] Furthermore, the preparation method of high-melting-point copolyester with a melting point of 270-290 ℃ is as follows: A high-melting-point copolyester with a melting point of 270-290 °C is obtained by esterification and polycondensation of refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate (CaCO3) in the presence of catalyst and stabilizer, followed by solid-phase thickening using a vacuum drum.

[0038] Furthermore, the weight ratio of terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate (CaCO3) is 20~60:10~30:30~80:0.1~0.5.

[0039] Furthermore, the esterification reaction temperature is 230~260 ℃, and the time is 2~5 h; the polycondensation reaction temperature is 270~300 ℃, and the vacuum degree is 10~100 Pa.

[0040] Furthermore, the calcium carbonate particles have a diameter of 0.6–1.0 μm and an ellipsoidal shape; the calcium carbonate particle size distribution index D50 is 0.8 μm.

[0041] Furthermore, the vacuum degree of vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h.

[0042] Furthermore, the catalyst and stabilizer are the same in the preparation methods of low-melting-point copolyesters with melting points of 160-200 ℃, medium-melting-point copolyesters with melting points of 220-230 ℃, and high-melting-point copolyesters with melting points of 270-290 ℃.

[0043] Furthermore, the catalyst is one or more of tetrabutyl titanate, germanium dioxide, and isopropyl titanate; the amount of catalyst used is 200-600 ppm based on the total weight of the acid system in the reaction system.

[0044] Furthermore, the stabilizer is one or more of trimethyl phosphate, dimethyl phosphate, tributyl phosphate, and triphenyl phosphate, and the amount of stabilizer used is 100-300 ppm based on the total weight of the acid system in the reaction system.

[0045] The total weight of the acid system refers to the sum of the weights of the acids in the system, which include: terephthalic acid (PTA), 2,6-naphthalenedicarboxylic acid (NDA), 2,5-furandicarboxylic acid (FDCA), and isophthalic acid (IPA).

[0046] Thirdly, the present invention provides the application of the hot melt composite film described in the first aspect in aluminum cup packaging.

[0047] Fourthly, the present invention provides a method for preparing an aluminum cup, the specific steps of which are as follows: The hot-melt composite film described in the first aspect is hot-melt bonded to a chrome-plated aluminum plate at a temperature of 200~260 ℃ and a pressure of 1000~3000 kg, and then the film is produced by deep pressing in a mold.

[0048] The aluminum cup was boiled in steam at 121 °C for 60 min, and the hot-melt composite film showed no peeling or whitening. It was also soaked in a 10% NaOH solution at room temperature for 72 h, and showed no peeling or discoloration. Furthermore, it was soaked in a 2% acetic acid and citric acid solution at room temperature for 72 h, and again in a 10% sodium chloride solution at room temperature for 72 h, without peeling or discoloration.

[0049] Compared with the prior art, the present invention has achieved the following beneficial effects: (1) The inner layer of this invention uses a low-melting-point copolyester with a melting point of 160-200 ℃, which has good thermal bonding properties with aluminum; the core layer uses a medium-melting-point copolyester with a melting point of 220-230 ℃, which has good resistance to impact, boiling and moisture; and the outer layer uses a high-melting-point copolyester with a melting point of 270-290 ℃, which has good resistance to acid, alkali and salt. In this invention, the inner layer, core layer and outer layer are melted and plasticized by a twin-screw extruder and then enter a three-layer distributor and a three-layer die head. The three-layer melt is instantaneously laminated at the die lip position of the three-layer "coat hanger" die head. After cooling by cooling rollers, air preheating, biaxial stretching and heat setting, a hot melt composite film for aluminum cups is obtained, which has great value for industrial production and practical application.

[0050] (2) The preparation method of this application is simple and easy to implement, has universality, and is easy to scale up for production. Detailed Implementation

[0051] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0052] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0053] Example 1 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 75:10:20:5:10. Based on the total weight of the acid system, 200 ppm tetrabutyl titanate and 100 ppm germanium dioxide composite were added as catalysts, and 300 ppm trimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 250 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 275 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 170 °C under a vacuum of 10 Pa for 72 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 180 °C.

[0054] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 35:25:50:4:10. Relative to the total weight of the acid system, 400 ppm germanium dioxide was added as a catalyst and 300 ppm trimethyl phosphate as a stabilizer for esterification. The esterification temperature was 252 °C, and the esterification time was 3 h. Subsequently, a polycondensation reaction was carried out at 280 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were then solid-phase thickening in a vacuum drum at 210 °C under a vacuum of 10 Pa for 72 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 220 °C.

[0055] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate with a particle size of 0.6 μm were mixed in a weight ratio of 30:35:60:0.5. 200 ppm tetrabutyl titanate was added as a catalyst and 300 ppm trimethyl phosphate as a stabilizer relative to the total weight of the acid system for esterification. The esterification temperature was 255 ℃ and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 285 ℃ under a vacuum of 10 Pa for 4 h. The mixture was granulated underwater to obtain chips, which were then solid-phase thickened at 280 ℃ in a vacuum drum at a vacuum of 10 Pa for 48 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 290 ℃.

[0056] The low-melting-point copolyester chips with a melting point of 180 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 250 °C, they become a melt. The melt passes through a 20 μm disc filter and is then fed into the inner layer of the three-layer adapter by a melt metering pump, finally reaching the inner layer of the three-layer "coat hanger" die.

[0057] The medium-melting-point copolyester chips with a melting point of 220 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 260 °C, they become a melt and pass through a 20 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0058] The high-melting-point copolyester chips with a melting point of 290 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 300 °C to become a melt. After passing through a 20 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0059] The inner, core, and outer layers of the prepared hot-melt composite film are stacked and flowed out at the die lip of the die head in a thickness ratio of 20:70:10. Under the force field of an electrostatic adsorption device of 10 kV and 6 mA, they are cooled by a quenching roller at 20 °C to form a 100 μm primary casting.

[0060] The 100 μm primary casting was preheated at 110 °C, simultaneously biaxially stretched at 120 °C (2.75 times longitudinal stretching and 3 times transverse stretching), heat-set at 180 °C, and cooled to form a 12 μm hot-melt composite film.

[0061] Example 2 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 80:15:15:5:5. Based on the total weight of the acid system, 150 ppm of isopropyl titanate and 250 ppm of germanium dioxide composite were added as a catalyst, and 200 ppm of triphenyl phosphate was added as a stabilizer for esterification. The esterification temperature was 240 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 280 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickened at 190 °C in a vacuum drum at a vacuum of 10 Pa for 72 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 200 °C.

[0062] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 33:28:48:4:7. Relative to the total weight of the acid system, 400 ppm germanium dioxide was added as a catalyst and 200 ppm triphenyl phosphate as a stabilizer for esterification. The esterification temperature was 240 °C and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 275 °C under a vacuum of 10 Pa for 4 h. The mixture was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 220 °C under a vacuum of 10 Pa for 72 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 230 °C.

[0063] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate with a particle size of 0.8 μm were mixed in a weight ratio of 30:35:65:0.3. Relative to the total weight of the acid system, 500 ppm tetrabutyl titanate was added as a catalyst and 200 ppm triphenyl phosphate as a stabilizer for esterification. The esterification temperature was 240 °C and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 290 °C under a vacuum of 10 Pa for 4 h. The mixture was granulated underwater to obtain chips, which were then solid-phase thickened at 280 °C under a vacuum of 10 Pa for 72 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 290 °C.

[0064] The low-melting-point copolyester chips with a melting point of 200 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 250 °C, they become a melt. The melt passes through a 30 μm disc filter and is then fed into the inner layer of the three-layer adapter by a melt metering pump, finally reaching the inner layer of the three-layer "coat hanger" die.

[0065] The medium-melting-point copolyester chips with a melting point of 230 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 260 °C, they become a melt and pass through a 30 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0066] The high-melting-point copolyester chips with a melting point of 290 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 310 °C to become a melt. After passing through a 30 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0067] The inner, core, and outer layers of the hot-melt composite film prepared in the previous steps are stacked and flowed out at the die lip of the die head in a ratio of 25:70:5. Under the force field of the electrostatic adsorption device of 12 kV and 7 mA, they are cooled by a quenching roller at 25°C to form a 100 μm primary casting.

[0068] The 100 μm primary casting was preheated at 120 °C, simultaneously biaxially stretched at 125 °C (2.5 times longitudinal stretching and 2 times transverse stretching), heat-set at 180 °C, and cooled to form a 20 μm hot melt composite film.

[0069] Example 3 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 70:15:20:15:3. Based on the total weight of the acid system, 350 ppm of a composite of isopropyl titanate and 150 ppm of tetrabutyl titanate were added as a catalyst, and 250 ppm of dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 255 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 285 °C under a vacuum of 20 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 185 °C under a vacuum of 20 Pa for 60 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 195 °C.

[0070] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 33:28:50:3:5. Relative to the total weight of the acid system, 100 ppm isopropyl titanate and 300 ppm germanium dioxide were added as catalysts, and 200 ppm dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 260 °C, and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 290 °C under a vacuum of 20 Pa for 4 h. The product was granulated underwater to obtain chips, which were then solid-phase thickened at 220 °C in a vacuum drum at a vacuum of 20 Pa for 60 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 230 °C.

[0071] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate (CaCO3) with a particle size of 1.0 μm were mixed in a weight ratio of 25:35:70:0.1. Relative to the total weight of the acid system, 450 ppm isopropyl titanate and 150 ppm tetrabutyl titanate were added as catalysts, and 300 ppm dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 260 °C, and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 310 °C under a vacuum of 20 Pa for 4 h. The product was granulated underwater to obtain chips, which were then solid-phase thickened at 285 °C in a vacuum drum at a vacuum of 20 Pa for 48 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 295 °C.

[0072] The low-melting-point copolyester chips with a melting point of 195 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 250 °C to become a melt. After passing through a 40 μm disc filter, the melt is fed into the inner layer of the three-layer adapter through a melt metering pump and finally reaches the inner layer of the three-layer "coat hanger" die.

[0073] The medium-melting-point copolyester chips with a melting point of 230 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 250 °C, they become a melt and pass through a 40 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0074] The high-melting-point copolyester chips with a melting point of 295 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 320 °C to become a melt. After passing through a 40 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0075] The inner, core, and outer layers of the hot-melt composite film prepared in the previous steps are stacked and flowed out at the die lip of the die head in a ratio of 15:75:10. Under the force field of an electrostatic adsorption device of 15 kV and 10 mA, they are cooled by a quenching roller at 30°C to form a primary casting of 112 μm.

[0076] The 112 μm primary casting was preheated at 125 °C, simultaneously biaxially stretched at 128 °C (3 times longitudinal stretching and 2.5 times transverse stretching), heat-set at 190 °C, and cooled to form a 15 μm hot-melt composite film.

[0077] The properties of the hot-melt composite films prepared in Examples 1-3 are shown in Table 1.

[0078] Table 1 Properties of hot melt composite films

[0079] Comparative Example 1 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 75:10:20:5:10. Based on the total weight of the acid system, 200 ppm tetrabutyl titanate and 100 ppm germanium dioxide composite were added as catalysts, and 300 ppm trimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 250 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 275 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 170 °C under a vacuum of 10 Pa for 72 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 180 °C.

[0080] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 35:25:50:4:10. Relative to the total weight of the acid system, 100 ppm germanium dioxide was added as a catalyst and 300 ppm trimethyl phosphate as a stabilizer for esterification. The esterification temperature was 252 °C, and the esterification time was 3 h. Subsequently, a polycondensation reaction was carried out at 280 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were then solid-phase thickened in a vacuum drum at 210 °C under a vacuum of 10 Pa for 72 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 220 °C.

[0081] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate with a particle size of 0.6 μm were mixed in a weight ratio of 30:35:60:0.5. Relative to the total weight of the acid system, 200 ppm tetrabutyl titanate was added as a catalyst and 200 ppm trimethyl phosphate as a stabilizer for esterification. The esterification temperature was 255 °C and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 285 °C under a vacuum of 10 Pa for 4 h. The mixture was granulated underwater to obtain chips, which were then solid-phase thickened at 280 °C under a vacuum of 10 Pa for 48 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 290 °C.

[0082] The low-melting-point copolyester chips with a melting point of 180 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 250 °C, they become a melt. The melt passes through a 20 μm disc filter and is then fed into the inner layer of the three-layer adapter by a melt metering pump, finally reaching the inner layer of the three-layer "coat hanger" die.

[0083] The medium-melting-point copolyester chips with a melting point of 220 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 260 °C, they become a melt and pass through a 20 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0084] The high-melting-point copolyester chips with a melting point of 290 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 300 °C to become a melt. After passing through a 20 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0085] The inner, core, and outer layers of the prepared hot-melt composite film are stacked and flowed out at the die lip of the die head in a thickness ratio of 10:80:10. Under the force field of an electrostatic adsorption device of 10 kV and 6 mA, they are cooled by a quenching roller at 20 °C to form a 100 μm primary casting.

[0086] The 100 μm primary casting was preheated at 110 °C, simultaneously biaxially stretched at 120 °C (2.75 times longitudinal stretching and 3 times transverse stretching), heat-set at 180 °C, and cooled to form a 12 μm hot-melt composite film.

[0087] Comparative Example 2 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 80:20:17:2:2. Based on the total weight of the acid system, 150 ppm of isopropyl titanate and 250 ppm of germanium dioxide composite were added as a catalyst, and 200 ppm of triphenyl phosphate was added as a stabilizer for esterification. The esterification temperature was 240 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 280 °C under a vacuum of 10 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 200 °C under a vacuum of 10 Pa for 72 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 210 °C.

[0088] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 33:28:48:4:7. Relative to the total weight of the acid system, 400 ppm germanium dioxide was added as a catalyst and 200 ppm triphenyl phosphate as a stabilizer for esterification. The esterification temperature was 240 °C and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 275 °C under a vacuum of 10 Pa for 4 h. The mixture was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 220 °C under a vacuum of 10 Pa for 72 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.2 dl / g and a melting point of 230 °C.

[0089] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate with a particle size of 0.8 μm were mixed in a weight ratio of 30:35:65:0.3. Relative to the total weight of the acid system, 500 ppm tetrabutyl titanate was added as a catalyst and 200 ppm triphenyl phosphate as a stabilizer for esterification. The esterification temperature was 240 °C and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 290 °C under a vacuum of 10 Pa for 4 h. The mixture was granulated underwater to obtain chips, which were then solid-phase thickened at 280 °C under a vacuum of 10 Pa for 72 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 290 °C.

[0090] The low-melting-point copolyester chips with a melting point of 210 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 250 °C to become a melt. After passing through a 30 μm disc filter, the melt is fed into the inner layer of the three-layer adapter through a melt metering pump and finally reaches the inner layer of the three-layer "coat hanger" die.

[0091] The medium-melting-point copolyester chips with a melting point of 230 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 260 °C, they become a melt and pass through a 30 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0092] The high-melting-point copolyester chips with a melting point of 290 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 310 °C to become a melt. After passing through a 30 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

[0093] The inner, core, and outer layers of the hot-melt composite film prepared in the previous steps are stacked and flowed out at the die lip of the die head in a ratio of 25:70:5. Under the force field of the electrostatic adsorption device of 12 kV and 7 mA, they are cooled by a quenching roller at 25°C to form a 100 μm primary casting.

[0094] The 100 μm primary casting was preheated at 120 °C, simultaneously biaxially stretched at 125 °C (2.5 times longitudinal stretching and 2 times transverse stretching), heat-set at 180 °C, and cooled to form a 20 μm hot melt composite film.

[0095] Comparative Example 3 Refined terephthalic acid (PTA), ethylene glycol (EG), 1,4-cyclohexanediethanol (CHDM), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 70:15:20:15:3. Based on the total weight of the acid system, 350 ppm of a composite of isopropyl titanate and 150 ppm of tetrabutyl titanate were added as a catalyst, and 250 ppm of dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 255 °C, and the esterification time was 3 h. Following this, a polycondensation reaction was carried out at 285 °C under a vacuum of 20 Pa for 4 h. The product was then granulated underwater to obtain chips, which were subsequently solid-phase thickening in a vacuum drum at 185 °C under a vacuum of 20 Pa for 60 h to obtain a low-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 195 °C.

[0096] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,5-furandicarboxylic acid (FDCA), isophthalic acid (IPA), and 1,4-dihydroxybutane (BDO) were mixed in a weight ratio of 33:28:50:3:5. Relative to the total weight of the acid system, 100 ppm isopropyl titanate and 300 ppm germanium dioxide were added as catalysts, and 200 ppm dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 260 °C, and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 290 °C under a vacuum of 20 Pa for 4 h. The product was granulated underwater to obtain chips, which were then solid-phase thickened at 220 °C in a vacuum drum at a vacuum of 20 Pa for 60 h to obtain a medium-melting-point copolyester with an intrinsic viscosity of 1.0 dl / g and a melting point of 230 °C.

[0097] Refined terephthalic acid (PTA), ethylene glycol (EG), 2,6-naphthalenedicarboxylic acid (NDA), and calcium carbonate with a particle size of 1.0 μm were mixed in a weight ratio of 75:35:10:0.1. Relative to the total weight of the acid system, 450 ppm isopropyl titanate and 150 ppm tetrabutyl titanate were added as catalysts, and 300 ppm dimethyl phosphate was added as a stabilizer for esterification. The esterification temperature was 260 °C, and the esterification time was 3 h. Then, a polycondensation reaction was carried out at 310 °C under a vacuum of 20 Pa for 4 h. The product was granulated underwater to obtain chips, which were then solid-phase thickened at 255 °C in a vacuum drum at a vacuum of 20 Pa for 48 h to obtain a high-melting-point copolyester with an intrinsic viscosity of 0.8 dl / g and a melting point of 265 °C.

[0098] The low-melting-point copolyester chips with a melting point of 195 °C obtained above are fed into a twin-screw extruder and melted and plasticized at 250 °C to become a melt. After passing through a 40 μm disc filter, the melt is fed into the inner layer of the three-layer adapter through a melt metering pump and finally reaches the inner layer of the three-layer "coat hanger" die.

[0099] The medium-melting-point copolyester chips with a melting point of 230 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 250 °C, they become a melt and pass through a 40 μm disc filter. They are then fed into the middle layer of the three-layer adapter by a melt metering pump and finally reach the core layer of the three-layer "coat hanger" die.

[0100] The high-melting-point copolyester chips with a melting point of 265 °C obtained above are fed into a twin-screw extruder. After being melted and plasticized at 275 °C, they become a melt. The melt passes through a 40 μm disc filter and is then fed into the outer layer of the three-layer adapter by a melt metering pump, finally reaching the outer layer of the three-layer "coat hanger" die.

[0101] The inner, core, and outer layers of the hot-melt composite film prepared in the previous steps are stacked and flowed out at the die lip of the die head in a ratio of 15:75:10. Under the force field of an electrostatic adsorption device of 15 kV and 10 mA, they are cooled by a quenching roller at 30°C to form a primary casting of 112 μm.

[0102] The 112 μm primary casting was preheated at 125 °C, simultaneously biaxially stretched at 128 °C (3 times longitudinal stretching and 2.5 times transverse stretching), heat-set at 190 °C, and cooled to form a 15 μm hot-melt composite film.

[0103] The properties of the hot-melt composite films prepared in Comparative Examples 1-3 are shown in Table 2.

[0104] Table 2 Comparative Properties of Hot-Melt Composite Films

[0105] Compared to Example 1, the thickness of the thick layer in Comparative Example 1 becomes 10:80:10, the heat-bonding layer (melting point layer at 180 ℃) becomes thinner, the thermal bonding strength with the aluminum cup deteriorates, and the film is easily peeled off; compared to Example 2, the melting point of the inner layer in Comparative Example 2 becomes 200 ℃ (180 ℃ in Example 2), the thermal bonding strength with the aluminum cup deteriorates, the film is easily peeled off, the resistance to boiling after bonding with the aluminum cup deteriorates, and it is easy to fall off after boiling; compared to Example 3, the melting point of the outer layer in Comparative Example 3 becomes 265 ℃ (295 ℃ in Example 3), the immersion test performance after bonding with the aluminum cup deteriorates, and it bubbles and easily falls off after immersion in NaCl, NaOH, acetic acid, and citric acid solutions.

[0106] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hot-melt composite film, characterized in that, The hot-melt composite film consists of an inner layer, a core layer, and an outer layer from the inside out; the inner layer is made of a low-melting-point copolyester with a melting point of 160-200 ℃; the core layer is made of a medium-melting-point copolyester with a melting point of 220-230 ℃; and the outer layer is made of a high-melting-point copolyester with a melting point of 270-290 ℃. The low-melting-point copolyester was prepared from terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, isophthalic acid, and 1,4-dihydroxybutane. The low-melting-point copolyester was prepared from terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, isophthalic acid, and 1,4-dihydroxybutane. The high-melting-point copolyester was prepared from terephthalic acid, ethylene glycol, 2,6-naphthalenedicarboxylic acid, and calcium carbonate. The thickness ratio of the three layers of the hot melt composite film is inner layer: core layer: outer layer = 15~30: 60~80: 5~15.

2. The hot-melt composite film as described in claim 1, characterized in that, The intrinsic viscosity of the low-melting-point copolyester is 0.80-1.2 dl / g; and / or, the intrinsic viscosity of the medium-melting-point copolyester is 0.80-1.5 dl / g; and / or, the intrinsic viscosity of the high-melting-point copolyester is 0.80-1.2 dl / g; and / or, the thickness of the hot-melt composite film is 10-20 μm.

3. The method for preparing the hot-melt composite film as described in claim 1, characterized in that, Includes the following steps: (1) Low melting point copolyester with a melting point of 160-200 ℃, medium melting point copolyester with a melting point of 220-230 ℃, and high melting point copolyester with a melting point of 270-290 ℃ are melted and plasticized by an extruder to become melts, which are then filtered and fed into the adapter to reach the inner layer, core layer and outer layer of the die head respectively. (2) The inner layer, core layer and outer layer melts are superimposed and flow out through the die head and then cooled to form a primary casting sheet; (3) The primary casting is preheated in air, biaxially stretched, heat-set and cooled to form a hot melt composite film.

4. The preparation method according to claim 3, characterized in that, In step (1), a disc filter with a thickness of 20~40 μm is used for filtration; and / or, in step (1), the adapter is a three-layer adapter; and / or, in step (1), the die head is a three-layer "coat hanger" die head; and / or, in step (2), the inner layer, core layer, and outer layer melts are superimposed and flow out at the die lip position of the die head; and / or, in step (2), a rapid cooling roller is used for cooling under the force field of the electrostatic adsorption device, the voltage of the electrostatic adsorption device is 10~20 kV; the current of the electrostatic adsorption device is 3~10 mA; the temperature after cooling is 10~40 ℃; and / or, in step (2), the thickness of the primary casting sheet is 100~200 μm.

5. The preparation method according to claim 3, characterized in that, In step (3), the thickness of the hot melt composite film is 10~20μm; and / or, in step (3), the primary casting is preheated at 80~120℃, biaxially stretched at 100~130℃, heat-set at 150~230℃, and cooled at 40~100℃ to form a 10~20 μm hot melt composite film; and / or, in step (3), the biaxial stretching is synchronous stretching; the biaxial stretching ratio is 1.5~3.0 times in the longitudinal direction and 1.5~3.0 times in the transverse direction; and / or, in step (3), the medium for biaxial stretching is hot air; the wind speed of the hot air for biaxial stretching is 10~30 m / s; and / or, the thickness ratio of the three layers of the hot melt composite film is inner layer: core layer: outer layer = 15~30: 60~80: 5~15.

6. The preparation method according to claim 3, characterized in that, The specific operation of step (1) is as follows: Low-melting-point copolyester chips with a melting point of 160-200 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the inner layer of the three-layer adapter and finally reaches the inner layer of the three-layer "coat hanger" die head. Medium-melting-point copolyester chips with a melting point of 220-230 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the middle layer of the three-layer adapter and finally reaches the core layer of the three-layer "coat hanger" die. High-melting-point copolyester chips with a melting point of 270-290 ℃ are fed into a twin-screw extruder and melted and plasticized into a melt. After passing through a 20-40 μm disc filter, the melt is pumped into the outer layer of the three-layer adapter and finally reaches the outer layer of the three-layer "coat hanger" die.

7. The preparation method according to claim 3, characterized in that, The preparation method of low-melting-point copolyester with melting point of 160-200 ℃ is as follows: terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, isophthalic acid, and 1,4-dihydroxybutane are subjected to esterification and polycondensation reactions in the presence of catalyst and stabilizer, and then solid-phase thickening is carried out by vacuum drum to obtain low-melting-point copolyester with melting point of 160-200 ℃; Preferably, the weight ratio of terephthalic acid, ethylene glycol, 1,4-cyclohexanediethanol, isophthalic acid, and 1,4-dihydroxybutane is 45~80:5~25:5~20:5~10:5~10; Preferably, the esterification reaction temperature is 230~260 ℃ and the time is 2~5 h; the polycondensation reaction temperature is 270~290 ℃ and the vacuum degree is 10~100 Pa. Preferably, the vacuum degree of vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h; And / or, the preparation method of medium melting point copolyester with melting point of 220-230 ℃ is as follows: terephthalic acid, ethylene glycol, 2,5-furandicarboxylic acid, isophthalic acid, and 1,4-dihydroxybutane are subjected to esterification and polycondensation reactions in the presence of catalyst and stabilizer, and then solid-phase thickening is carried out by vacuum drum to obtain medium melting point copolyester with melting point of 220-230 ℃; Preferably, the weight ratio of terephthalic acid, ethylene glycol, 2,5-furandicarboxylic acid, isophthalic acid and 1,4-dihydroxybutane is 30~80:5~25:10~60:4~10:1~5; Preferably, the esterification reaction temperature is 230~260 ℃ and the time is 1~3 h; the polycondensation reaction temperature is 260~290 ℃ and the vacuum degree is 20~100 Pa. Preferably, the vacuum degree of vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h; And / or, the preparation method of high melting point copolyester with melting point of 270-290 ℃ is as follows: terephthalic acid, ethylene glycol, 2,6-naphthalenedicarboxylic acid and calcium carbonate are subjected to esterification and polycondensation reaction in the presence of catalyst and stabilizer, and then high melting point copolyester with melting point of 270-290 ℃ is obtained by solid-phase thickening using vacuum drum. Preferably, the weight ratio of terephthalic acid, ethylene glycol, 2,6-naphthalenedicarboxylic acid, and calcium carbonate is 20~60:10~30:30~80:0.1~0.5; Preferably, the esterification reaction temperature is 230~260 ℃ and the time is 2~5 h; the polycondensation reaction temperature is 270~300 ℃ and the vacuum degree is 10~100 Pa. Preferably, the calcium carbonate particle size is 0.6~1.0 μm, and the shape is ellipsoidal; the calcium carbonate particle size distribution index D50 is 0.8 μm. And / or, the vacuum degree for vacuum solid-phase thickening is 10~30 Pa; the vacuum solid-phase thickening time is 48~72 h.

8. The preparation method according to claim 7, characterized in that, The catalyst is one or more of tetrabutyl titanate, germanium dioxide, and isopropyl titanate; preferably, the amount of catalyst used is 200-600 ppm based on the total weight of the acid system in the reaction system. And / or, the stabilizer is one or more of trimethyl phosphate, dimethyl phosphate, tributyl phosphate, and triphenyl phosphate. Preferably, the amount of stabilizer used is 100 to 300 ppm based on the total weight of the acid system in the reaction system.

9. The application of the hot melt composite film as described in any one of claims 1 to 2 in aluminum cup packaging.

10. A method for preparing an aluminum cup, characterized in that, The steps are as follows: The hot-melt composite film according to any one of claims 1 to 2 is hot-melt bonded to a chromium-plated aluminum plate at a temperature of 200 to 260 °C and a pressure of 1000 to 3000 kg, and then the film is produced by deep pressing in a mold.

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