A packaging composite film with good barrier property, high kink resistance and low resilience and a preparation method thereof

Abstract

This invention discloses a composite film for packaging with good barrier properties, high kink strength, and low resilience, as well as its preparation method, belonging to the technical field of composite film preparation. The raw materials of this invention include: 45-55 parts PET, 25-40 parts PP, 0.5-1 part heat stabilizer, 2-5 parts antioxidant, 2-3 parts ultraviolet absorber; 1-2 parts hindered amine light stabilizer, 2-3 parts lubricant, 4-6 parts coupling agent, 5-10 parts filler, 1-2 parts flame retardant, 5-8 parts crosslinking agent, and 2-8 parts compatibilizer. By adding the compatibilizer PP-g-MAH, the compatibility of the PET / PP blend system can be improved, thereby enhancing its rheological and mechanical properties.

Description

Technical Field

[0001] This invention belongs to the technical field of composite film preparation, and particularly relates to a packaging composite film with good barrier properties, high kink strength and low resilience, and its preparation method. Background Technology

[0002] Twist packaging is one of the most traditional candy packaging methods, along with pillow packaging and folding packaging, forming the three major candy packaging methods. In the overall candy packaging landscape, pillow packaging accounts for approximately 70%, twist packaging for about 15%, folding packaging for about 10%, and other packaging methods for about 5%. Twist packaging is the oldest candy packaging method. Initially, it used paper (cellophane) and was handmade. With the advent and widespread adoption of mechanized pillow packaging machines, pillow packaging became popular due to its low cost. However, pillow packaging, with its uniformity and lack of aesthetic appeal, has limitations. Therefore, high-end, high-quality candies often use more personalized twisted film or folding paper.

[0003] The development of twist film has spanned over 20 years, initially focusing on PVC twist film and some imported cellophane. Research and promotion of a new, environmentally friendly PET twist film began in 2002-2003 to replace toxic PVC twist products. However, due to cost and profit considerations, PVC film did not completely disappear from the food packaging industry until the plasticizer scandal made various sectors of society and factories aware of the hazards of PVC twist products, leading to the widespread application of PET products.

[0004] The replacement of PVC twist film with PET twist film is an inevitable trend. Its product performance has unparalleled advantages. The advantages of PET twist film include environmental friendliness, economy, high efficiency, stable performance, safety, and aesthetics. Environmental friendliness: PET twist film is made of polyester, an environmentally friendly and recyclable product that poses no harm to humans or the environment. In contrast, PVC products release dimethane when burned, a substance that can cause cancer. In Europe and America, PVC products are strictly prohibited from contact with food, and some of the strictest Western European countries even ban PVC film from being used for the outer packaging of children's products. Economy and efficiency: Traditional PVC products must be at least 28μm thick to have sufficient hardness and stiffness to meet the requirements for metallization and printing, thus achieving a rigid product effect. PET products, due to their sufficient strength and stiffness, can be produced in thicknesses of 19μm, 23μm, and 25μm. 19μm is mainly used for handmade packaging of dried meat, fresh fruit packaging, or paper-plastic composite twist packaging. 23μ and 25μ are mainly used for twisted packaging of candies and chocolates; stable performance and high efficiency: PVC packaging machines have a maximum speed of 1000 pieces / minute, while PET can reach 2000 pieces / minute. Due to its brittle material and poor flatness, PVC products are generally limited to a film width of around 60cm, while PET products can have a limited printing film width of over one meter. PET printing speeds can reach over 200m / minute, while PVC cannot exceed 150m / minute. Therefore, PET products have a clear advantage in printing efficiency; aesthetically pleasing and high-end: PET twisted film has a stronger aluminum layer, and adding protective resin (gold ink) during the printing process can make the printed pattern bright and clear; at the same time, utilizing the high rigidity and corrosion resistance of PET, partial aluminum washing or laser effect treatment can be applied, resulting in a strong three-dimensional effect and greatly improving the grade of the packaged products.

[0005] Therefore, the main material for twist packaging has shifted from PVC to environmentally friendly PET twist film. While PET twist film offers good transparency and gloss, allowing for a more visually appealing and aesthetically pleasing presentation of packaged items, and is free of halogens, complying with food safety regulations, making it a viable alternative to traditional PVC twist film, its current production suffers from poor impact resistance, environmental stress cracking resistance, and barrier properties. Furthermore, its high material cost and significant equipment investment hinder its widespread adoption. PP (polypropylene) is a tough and easy-to-process material, producing films that are cost-effective. However, its good toughness and deformation recovery characteristics generally make it difficult to use directly in twist film production. Under certain conditions, however, adding PP can improve the mechanical properties and barrier properties of PET, enhancing the impact resistance and environmental durability of PET twist film.

[0006] Therefore, in the process of preparing PET twisted film, how to modify PET with PP so that the two can be effectively combined to form a composite film with high twist strength and low resilience has become an urgent problem to be solved. Summary of the Invention

[0007] The primary objective of this invention is to disclose a composite film for packaging that has good barrier properties, high kink strength, and low resilience. While possessing good barrier properties and high kink strength, it also has low resilience, enabling it to effectively package products.

[0008] The second objective of this invention is to disclose a method for preparing a composite film for packaging with high kink strength and low resilience. By using PP to improve the processing impact resistance, environmental stress cracking resistance and barrier properties of PET, PET can also improve the strength, heat resistance and surface hardness of PP. The two interact to jointly improve the kink performance and barrier properties of the composite film.

[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0010] A composite film for packaging with good barrier properties, high kink strength, and low resilience, comprising the following raw materials by weight: 45-55 parts PET, 25-40 parts PP, 0.5-1 part heat stabilizer, 2-5 parts antioxidant, 2-3 parts ultraviolet absorber; 1-2 parts hindered amine light stabilizer, 2-3 parts lubricant, 4-6 parts coupling agent, 5-10 parts filler, 1-2 parts flame retardant, 5-8 parts crosslinking agent, and 2-8 parts compatibilizer.

[0011] Furthermore, by weight, the raw materials include: 55 parts PET, 40 parts PP, 1 part heat stabilizer, 5 parts antioxidant, 2 parts ultraviolet absorber; 2 parts hindered amine light stabilizer, 3 parts lubricant, 6 parts coupling agent, 6 parts filler, 2 parts flame retardant, 5 parts crosslinking agent, and 8 parts compatibilizer.

[0012] Further, the heat stabilizer is FT-4288; the antioxidant is selected from diphenylamine and p-phenylenediamine; the ultraviolet absorber is selected from 2-hydroxy-4-methoxybenzophenone and 2-(2-hydroxy-3,5-bis(a,a-dimethylbenzyl)phenyl)benzotriazole; and the hindered amine light stabilizer is selected from (2,2,6,6-tetramethyl-4-hydroxypiperidine) benzoate and tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite.

[0013] Furthermore, the lubricant is pentaerythritol stearate; the coupling agent is isopropyl dioleoyloxy (dioctyl phosphate oxy) titanate; and the filler is silicon dioxide.

[0014] Furthermore, the crosslinking agent is oleamide; the flame retardant is TDBPPE.

[0015] Furthermore, the compatibilizer is PP-g-MAH.

[0016] Furthermore, the preparation method of any of the above-mentioned composite films for packaging with good barrier properties, high kink strength, and low resilience includes the following steps:

[0017] (1) PET, FT-4288, diphenylamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate, isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 25-35 min. Then the mixture is transferred to an internal mixer and internally mixed for 15-20 min. After cooling naturally to 70-90°C, it is taken out, chopped, and then cooled to room temperature to obtain modified PET granules.

[0018] (2) The modified PET granules, PP, oleamide and PP-g-MAH are mixed and added to a twin-screw extruder for extrusion granulation to obtain mixed granules;

[0019] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm. Then, perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0020] Furthermore, in step (1), the temperature of the internal mixer is 240~290℃ and the rotation speed is 50r / min.

[0021] Furthermore, in step (2), the extrusion temperature of the twin-screw extruder is 180~220℃.

[0022] Furthermore, in step (3), the temperature of the extrusion casting machine is 200~220℃.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1) This invention uses PP and PET composites to prepare kinked films. By adding the compatibilizer PP-g-MAH, the compatibility of the PET / PP blend system can be improved, thereby enhancing its rheological and mechanical properties. The addition of the compatibilizer not only improves the flow properties of the PET / PP alloy but also reduces the influence of shear rate on apparent viscosity, thus reducing the material's dependence on temperature.

[0025] 2) By adding heat stabilizers to the raw materials, the present invention can effectively reduce the melt viscosity of PET and improve its fluidity; at the same time, it can improve the physical properties of PET through its specific chemical structure, such as enhancing its impact resistance and increasing its heat deformation temperature.

[0026] 3) The PET composite twisted film prepared by this invention has excellent physical properties and chemical stability, which can meet the requirements of high-speed printing machines and twisted packaging machinery. At the same time, it has good high temperature resistance and low shrinkage rate, ensuring its stability and packaging tightness in high temperature environment. In addition, the PET composite twisted film also has antistatic properties and excellent printing quality, making it suitable for various packaging needs. Detailed Implementation

[0027] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0028] Unless otherwise specified, all raw materials or components used in the following embodiments were purchased commercially available.

[0029] The methods for testing the various properties of the composite membranes obtained in the following embodiments and comparative examples are as follows:

[0030] Tensile property testing: The electronic universal testing machine uses a dedicated pneumatic clamp for thin films, with a force sensor range of 100N. The film is cut into 200mm x 15mm specimens, and its tensile properties are tested according to ASTM D638-03. The tensile speed is 500mm / min.

[0031] Optical performance testing: transmittance was tested according to GB / T2410-2008, and gloss was tested according to ASTMD2457-2008.

[0032] Knot test: Fold a small piece of film sample once along the centerline, fix one end of the film, rotate the other end 360 degrees, then release the sample to allow it to spring back freely, and finally measure the kink retention angle (RA).

[0033] Example 1

[0034] A composite film for packaging with good barrier properties, high kink strength, and low resilience comprises the following raw materials in parts by weight: 55 parts PET (average molecular weight 40,000~50,000), 25 parts PP, 0.5 parts FT-4288, 2 parts p-phenylenediamine, 2 parts 2-hydroxy-4-methoxybenzophenone, 3 parts pentaerythritol stearate, 5 parts isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, 5~10 parts silica, 2 parts TDBPPE, 8 parts oleamide, and 5 parts PP-g-MAH;

[0035] The preparation method of the above composite membrane includes the following steps:

[0036] (1) PET (average molecular weight of 40,000~50,000), FT-4288, p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate, isopropyl dioleoyl oxy(dioctyl phosphate oxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 25 min. Then the mixture is transferred to an internal mixer and internally mixed at 240℃ and 50 r / min for 15 min. After that, it is naturally cooled to 80℃, taken out and chopped, and then cooled to room temperature to obtain modified PET granules.

[0037] (2) The modified PET granules, PP, oleamide and PP-g-MAH were mixed and added to a twin-screw extruder. The mixture was melt-extruded and granulated at 210℃ and 250r / min to obtain mixed granules.

[0038] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 200℃. Then perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0039] Example 2

[0040] A composite film for packaging with good barrier properties, high kink strength, and low resilience comprises the following raw materials in parts by weight: 50 parts PET (average molecular weight 40,000~50,000), 30 parts PP, 1 part FT-4288, 5 parts diphenylamine, 3 parts 2-(2-hydroxy-3,5-bis(a,a-dimethylbenzyl)phenyl)benzotriazole; 2 parts tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite, 2 parts pentaerythritol stearate, 4 parts isopropyl dioleoyloxy(dioctylphosphoyloxy)titanate, 8 parts silica, 2 parts TDBPPE, 5 parts oleamide, and 8 parts PP-g-MAH;

[0041] The preparation method of the above composite membrane includes the following steps:

[0042] (1) PET (average molecular weight of 40,000~50,000), FT-4288, diphenylamine, 2-(2-hydroxy-3,5-bis(a,a-dimethylbenzyl)phenyl)benzotriazole, tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphate, pentaerythritol stearate, isopropyl dioleoyloxy(dioctylphosphoyloxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 30 min. Then the mixture is transferred to an internal mixer and internally mixed at 260°C and 50 r / min for 15 min. After cooling naturally to 70°C, the mixture is taken out, chopped, and then cooled to room temperature to obtain modified PET granules.

[0043] (2) The modified PET granules, PP, oleamide and PP-g-MAH were mixed and added to a twin-screw extruder. The mixture was melt-extruded and granulated at 200℃ and 250r / min to obtain mixed granules.

[0044] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 210℃. Then perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0045] Example 3

[0046] A composite film for packaging with good barrier properties, high kink strength, and low resilience comprises the following raw materials in parts by weight: 55 parts PET (average molecular weight 40,000~50,000), 40 parts PP, 1 part FT-4288, 5 parts p-phenylenediamine, 2 parts 2-hydroxy-4-methoxybenzophenone; 2 parts benzoate (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, 3 parts pentaerythritol stearate, 6 parts isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, 6 parts silica, 2 parts TDBPPE, 5 parts oleamide, and 8 parts PP-g-MAH;

[0047] A method for preparing a packaging composite film with good barrier properties, high kink strength, and low resilience, comprising the following steps:

[0048] (1) PET (average molecular weight of 40,000~50,000), FT-4288, p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate, isopropyl dioleoyl oxy(dioctyl phosphate oxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 30 min. Then the mixture is transferred to an internal mixer and internally mixed at 240℃ and 50 r / min for 15 min. After that, it is naturally cooled to 90℃, taken out and chopped, and then cooled to room temperature to obtain modified PET granules.

[0049] (2) The modified PET granules, PP, oleamide and PP-g-MAH were mixed and added to a twin-screw extruder. The mixture was melt-extruded and granulated at 220°C and 250 r / min to obtain mixed granules.

[0050] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 210℃. Then perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0051] Example 4

[0052] A composite film for packaging with good barrier properties, high kink strength, and low resilience comprises the following raw materials in parts by weight: 48 parts PET (average molecular weight 40,000~50,000), 32 parts PP, 1 part FT-4288, 5 parts diphenylamine, 3 parts 2-hydroxy-4-methoxybenzophenone; 2 parts (2,2,6,6-tetramethyl-4-hydroxypiperidine) benzoate, 3 parts pentaerythritol stearate, 5 parts isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, 7 parts silica, 2 parts TDBPPE, 5 parts oleamide, and 8 parts PP-g-MAH;

[0053] A method for preparing a packaging composite film with good barrier properties, high kink strength, and low resilience, comprising the following steps:

[0054] (1) PET (average molecular weight of 40,000~50,000), FT-4288, diphenylamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate, isopropyl dioleoyl oxy(dioctyl phosphate oxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 35 min. Then the mixture is transferred to an internal mixer and internally mixed at 290℃ and 50 r / min for 20 min. After that, it is naturally cooled to 70℃, taken out and chopped, and then cooled to room temperature to obtain modified PET granules.

[0055] (2) The modified PET granules, PP, oleamide and PP-g-MAH were mixed and added to a twin-screw extruder. The mixture was melt-extruded and granulated at 180°C and 250 r / min to obtain mixed granules.

[0056] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 200℃. Then perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0057] Example 5

[0058] A composite film for packaging with good barrier properties, high kink strength, and low resilience comprises the following raw materials in parts by weight: 55 parts PET (average molecular weight 40,000~50,000), 38 parts PP, 0.5~1 parts FT-4288, 2~5 parts p-phenylenediamine, 2 parts 2-hydroxy-4-methoxybenzophenone; 1 part tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite, 3 parts pentaerythritol stearate, 4 parts isopropyl dioleoyloxy(dioctylphosphoyloxy) titanate, 6 parts silica, 1 part TDBPPE, 7 parts oleamide, and 5 parts PP-g-MAH;

[0059] A method for preparing a packaging composite film with good barrier properties, high kink strength, and low resilience, comprising the following steps:

[0060] (1) PET (average molecular weight of 40,000~50,000), FT-4288, p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite, pentaerythritol stearate, isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 35 min. Then the mixture is transferred to an internal mixer and internally mixed at 250°C and 50 r / min for 15 min. After cooling naturally to 75°C, the mixture is taken out, chopped, and then cooled to room temperature to obtain modified PET granules.

[0061] (2) The modified PET granules, PP, oleamide and PP-g-MAH were mixed and added to a twin-screw extruder. The mixture was melt-extruded and granulated at 210℃ and 250r / min to obtain mixed granules.

[0062] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 200℃. Then perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

[0063] Comparative Example 1

[0064] A 15 μm thick PET twisted film was prepared using conventional methods.

[0065] Comparative Example 2

[0066] A composite film for packaging comprises the following raw materials in parts by weight: 55 parts PET (average molecular weight of 40,000~50,000) FT-4288 1 part, p-phenylenediamine 5 parts, pentaerythritol stearate 3 parts, isopropyl dioleoyl oxy(dioctyl phosphate oxy) titanate 6 parts, silica 6 parts, TDBPPE 2 parts, oleamide 5 parts, and PP-g-MAH 8 parts;

[0067] The preparation method of the above-mentioned composite film for packaging includes the following steps:

[0068] (1) PET (average molecular weight of 40,000~50,000), FT-4288, p-phenylenediamine, pentaerythritol stearate, isopropyl dioleoyl oxy (dioctyl phosphate oxy) titanate, silica, TDBPPE, oleamide and PP-g-MAH are added to a high-speed mixer and mixed at 250 r / min for 30 min. Then the mixture is transferred to an internal mixer and internally mixed at 240℃ and 50 r / min for 15 min. After that, it is naturally cooled to 90℃, taken out and chopped, and then cooled to room temperature to obtain modified PET granules.

[0069] (2) The modified PET granules are placed in an extrusion casting machine and cast into a film with a thickness of 15μm at 210℃. Then, double-sided corona treatment is performed and the film is wound up to obtain a PET twisted film.

[0070] Comparative Example 3

[0071] A composite film for packaging comprises the following raw materials in parts by weight: 55 parts PET (average molecular weight 40,000~50,000), 1 part FT-4288, 5 parts p-phenylenediamine, 2 parts 2-hydroxy-4-methoxybenzophenone; 2 parts benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, 3 parts pentaerythritol stearate, and 6 parts isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate;

[0072] The preparation method of the above-mentioned composite film for packaging includes the following steps:

[0073] (1) PET (average molecular weight of 40,000~50,000), FT-4288, p-phenylenediamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate and isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate were added to a high-speed mixer and mixed at 250 r / min for 30 min. Then the mixture was transferred to an internal mixer and internally mixed at 240°C and 50 r / min for 15 min. After cooling naturally to 90°C, the mixture was taken out, chopped, and then cooled to room temperature to obtain modified PET granules.

[0074] (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm at 210℃. Then, perform double-sided corona treatment and roll them up to obtain a PET twisted film.

[0075] The kink films obtained in the above embodiments and comparative examples were subjected to tensile property tests, optical property tests, and kink tests, and the test results are shown in Table 1 below.

[0076]

[0077] As can be seen from the data in Table 1, the composite twisted films prepared in Examples 1-5 are superior to the comparative examples in terms of tensile strength, optical properties, and twisting performance, indicating that the composite twisted films prepared by this invention have better advantages as packaging materials. The PET used in this invention can improve the strength, modulus, heat resistance, and surface hardness of PP, while PP can improve the processing impact resistance, environmental stress cracking resistance, and barrier properties of PET. The aim is to strengthen, toughen, and harden the material, while simultaneously improving its wear resistance, pressure resistance, and impact resistance.

[0078] Among them, the tensile strength and kink retention angle of the composite kink film prepared in Example 3 were higher than those of the other examples, indicating that appropriately increasing the PP content and the proportion of compatibilizer during the preparation of the composite material can effectively improve the kink strength and tensile properties of the kink composite film. This may be because adding the compatibilizer PP-g-MAH can improve the compatibility of the PET / PP blend system, thereby improving its rheological and mechanical properties. The addition of the compatibilizer not only improves the flow properties of the PET / PP alloy but also reduces the influence of shear rate on apparent viscosity, thus reducing the material's dependence on temperature.

[0079] 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 composite film for packaging, characterized in that, By weight, the raw materials include: 45-55 parts PET, 25-40 parts PP, 0.5-1 part heat stabilizer, 2-5 parts antioxidant, 2-3 parts UV absorber, 1-2 parts hindered amine light stabilizer, 2-3 parts lubricant, 4-6 parts coupling agent, 5-10 parts filler, 1-2 parts flame retardant, 5-8 parts crosslinking agent, and 2-8 parts compatibilizer; the heat stabilizer is FT-4288; the antioxidant is selected from diphenylamine and p-phenylenediamine; the UV absorber is selected from 2-hydroxy-4-methoxybenzophenone and 2-(2-hydroxy-3,5-bis(a,a-diphenylamine)). The product is selected from one of (methylbenzyl)phenyl)benzotriazole; the hindered amine light stabilizer is selected from one of (2,2,6,6-tetramethyl-4-hydroxypiperidine) benzoate and tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite; the lubricant is pentaerythritol stearate; the coupling agent is isopropyl dioleoyloxy(dioctylphosphoyloxy) titanate; the filler is silica; the crosslinking agent is oleamide; the flame retardant is TDBPPE; and the compatibilizer is PP-g-MAH.

2. The composite film for packaging according to claim 1, characterized in that, By weight, the raw materials include: 55 parts PET, 40 parts PP, 1 part heat stabilizer, 5 parts antioxidant, 2 parts UV absorber, 2 parts hindered amine light stabilizer, 3 parts lubricant, 6 parts coupling agent, 6 parts filler, 2 parts flame retardant, 5 parts crosslinking agent, and 8 parts compatibilizer.

3. A method for preparing a composite film for packaging as described in claim 1 or 2, characterized in that, The steps are as follows: (1) PET, FT-4288, diphenylamine, 2-hydroxy-4-methoxybenzophenone, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, pentaerythritol stearate, isopropyl dioleoyloxy (dioctylphosphoyloxy) titanate, silica and TDBPPE are added to a high-speed mixer and mixed at 250 r / min for 25-35 min. Then the mixture is transferred to an internal mixer and internally mixed for 15-20 min. After cooling naturally to 70-90°C, it is taken out, chopped, and then cooled to room temperature to obtain modified PET granules. (2) The modified PET granules, PP, oleamide and PP-g-MAH are mixed and added to a twin-screw extruder for extrusion granulation to obtain mixed granules; (3) Place the mixed granules in an extrusion casting machine and cast them into a film with a thickness of 15μm. Then, perform double-sided corona treatment and roll them up to obtain a PET-PP composite twisted film.

4. The method according to claim 3, characterized in that, In step (1), the temperature of the internal mixer is 240~290℃ and the rotation speed is 50r / min.

5. The method according to claim 3, characterized in that, In step (2), the extrusion temperature of the twin-screw extruder is 180~220℃.

6. The method according to claim 3, characterized in that, In step (3), the temperature of the extrusion casting machine is 200~220℃.

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