A composite film for heat sealing of plastic cups and a preparation method thereof

Abstract

The application relates to the technical field of antioxidant active sealing film, and discloses a composite film for plastic cup heat sealing and a preparation method, specifically, an outer layer formula is 60-80 wt% high-density polyethylene resin and 20-40 wt% linear low-density polyethylene resin, and the amount is 20-30 parts by weight; a middle layer formula is 70-90 wt% high-density polyethylene resin and 10-30 wt% linear low-density polyethylene resin, and the amount is 40-60 parts by weight; and an inner layer formula is 60-80 wt% low-density polyethylene resin and 20-40 wt% antioxidant active polyethylene master batch, and the amount is 20-30 parts by weight. The prepared film product can hardly release the loaded antioxidant under the condition of no heat sealing, and the heat sealing process can trigger the release of the antioxidant, so that the prepared film product can provide antioxidant protection for the cup-packed fresh fruit juice product completed by heat sealing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antioxidant active sealing film, in particular to a plastic cup hot sealing composite film with antioxidant active sealing function and a preparation method thereof. BACKGROUND

[0002] Currently, the packaging method mainly used for fresh juice products delivered to consumers through a take-out platform is a plastic cup made of disposable food-grade polypropylene (PP) material. In order to prevent juice leakage during delivery, a sealing film is usually installed on the cup mouth by a heat sealing machine.

[0003] Fresh juice products are rich in vitamins, polyphenols, chlorophyll, anthocyanins and aromatic substances that are easily oxidized by oxygen. In particular, for fresh juice products that emphasize zero addition and cannot use antioxidant additives, even if a common sealing film (such as a PP / PE film) is used to seal the cup mouth, it can play a physical barrier role in delaying microbial contamination and external contamination, but it cannot effectively prevent the oxidation of fresh juice products caused by the oxygen in the headspace of the cup and the trace of oxygen permeating through the packaging. Therefore, for oxidation-sensitive fresh juice products, simple physical sealing is far from enough. Instead, providing antioxidant active sealing film for the cup mouth can ensure the freshness, taste and nutritional value of fresh juice products delivered to consumers. This not only extends the quality control of fresh juice products to the last link, but also provides a new feasible solution for the core pain point of the fresh juice product delivery industry from the perspective of packaging technology. SUMMARY

[0004] The present application independently develops a plastic cup hot sealing composite film with antioxidant active sealing function that is compatible with food-grade polypropylene material plastic cups. The food-grade antioxidant loaded in the film is released into the sealed space between the sealing film and the cup mouth through a heat sealing process, thereby achieving the technical effect of providing antioxidant protection for cup-packed fresh juice products.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A plastic cup hot sealing composite film, the product structure of the composite film is:

[0007] Outer layer: the formula is 60-80wt% high density polyethylene resin and 20-40wt% linear low density polyethylene resin, the amount is 20-30 parts by weight;

[0008] Middle layer: the formula is 70-90wt% high density polyethylene resin and 10-30wt% linear low density polyethylene resin, the amount is 40-60 parts by weight;

[0009] The inner layer is prepared from 60-80 wt% low-density polyethylene resin and 20-40 wt% antioxidant active polyethylene masterbatch, and the amount of the antioxidant active polyethylene masterbatch is 20-30 parts by weight;

[0010] The preparation method of the antioxidant active polyethylene masterbatch is as follows:

[0011] Based on the condensation reaction mechanism of silicon hydroxyl groups, long-chain alkyl phenyl silane coupling agents are modified onto diatomite rich in silicon hydroxyl groups to obtain long-chain alkyl phenyl functionalized diatomite.

[0012] The long-chain alkyl phenyl functionalized diatomite physically adsorbs the phenyl-containing food-grade antioxidant through the internal pores and adsorbs the antioxidant through the π-π stacking effect between the surface rich in phenyl groups and the antioxidant to obtain long-chain alkylated antioxidant diatomite.

[0013] During the melt blending process, the long-chain alkyl groups on the surface of the long-chain alkylated antioxidant diatomite and the molecular chains of the linear low-density polyethylene resin are mutually diffused and entangled, realizing the uniform dispersion and firm combination of the diatomite in the linear low-density polyethylene resin matrix to obtain the antioxidant active polyethylene masterbatch.

[0014] Preferably, the mass ratio of diatomite to long-chain alkyl phenyl silane coupling agent in the long-chain alkyl phenyl functionalized diatomite is 1:0.075-0.15.

[0015] Preferably, the mass ratio of long-chain alkyl phenyl functionalized diatomite to phenyl-containing food-grade antioxidant in the long-chain alkylated antioxidant diatomite is 1:1.5-2.5.

[0016] Preferably, the mass ratio of linear low-density polyethylene resin to long-chain alkylated antioxidant diatomite in the antioxidant active polyethylene masterbatch is 1:0.05-0.15.

[0017] Preferably, the phenyl-containing food-grade antioxidant is one of carvacol and alpha-tocopherol.

[0018] Preferably, the thickness of the composite film is 30-80 μm.

[0019] A preparation method of a composite film for heat sealing of plastic cups, comprising the following steps:

[0020] According to the formula, the raw materials of each layer are fed into the hoppers of the three single-screw extruders of a three-layer co-extrusion film blowing machine set, the molten resins are converged at the die head through a flow divider, and then the composite film is prepared through extrusion blowing, cooling, and winding.

[0021] The temperature of each zone of the single screw extruder corresponding to the outer layer is: zone 1 115-125 DEG C, zone 2 145-160 DEG C, zone 3 170-180 DEG C, the flow channel temperature is 160-170 DEG C, and the screw rotation speed is 25-35 r / min.

[0022] The temperature of each zone of the single screw extruder corresponding to the intermediate layer is: zone 1 115-125 DEG C, zone 2 150-165 DEG C, zone 3 170-180 DEG C, the flow channel temperature is 160-170 DEG C, and the screw rotation speed is 30-40 r / min.

[0023] The temperature of each zone of the single screw extruder corresponding to the inner layer is: zone 1 105-115 DEG C, zone 2 140-155 DEG C, zone 3 155-165 DEG C, the flow channel temperature is 145-155 DEG C, and the screw rotation speed is 20-30 r / min.

[0024] Preferably, the preparation method of the long-chain alkyl phenyl silane coupling agent is as follows:

[0025] Based on the Friedel-Crafts alkylation reaction mechanism, under the catalysis of Lewis acid, octaphenyl-POSS is used as raw material, first, electrophilic substitution reaction occurs between the phenyl functional group and the alkenyl functional group of long straight chain alpha-olefin, then electrophilic substitution reaction occurs between the remaining phenyl functional group and the alkenyl functional group of vinyl trimethoxysilane, and the molar ratio of octaphenyl-POSS, long straight chain alpha-olefin and vinyl trimethoxysilane participating in the reaction is controlled to be 1:0.95-0.99:0.95-0.99, so that the long-chain alkyl phenyl silane coupling agent is synthesized; wherein the long straight chain alpha-olefin is one of 1-tetradecene, 1-hexadecene and 1-octadecene.

[0026] Preferably, the Lewis acid is one of anhydrous AlCl3 and anhydrous FeCl3.

[0027] The application of a plastic cup heat-seal composite film triggers the release of antioxidants into the sealed space of the plastic cup through a heat-seal process, providing antioxidant protection for cup-packed fresh fruit juice products.

[0028] The application has the following beneficial effects:

[0029] Under the catalysis of Lewis acid, octaphenyl-POSS is used as raw material, and long-chain alkyl phenyl silane coupling agent is synthesized through step-by-step Friedel-Crafts alkylation reaction, and the specific process is as follows:

[0030] First, long-chain alkyl groups are introduced by reacting phenyl groups in 1 mole equivalent of octa-phenyl-POSS with a slight excess (0.95-0.99 mole equivalent) of long straight-chain alpha-olefin; then the remaining phenyl groups in 1 mole equivalent of octa-phenyl-POSS are reacted with a slight excess (0.95-0.99 mole equivalent) of vinyltrimethoxysilane to introduce silane coupling groups;

[0031] The long-chain alkyl phenyl silane coupling agent is modified to the surface of diatomite rich in silicon hydroxyl groups, then the diatomite physically adsorbs the phenyl-containing food-grade antioxidant through the internal pore-rich diatomite, and the diatomite surface rich in phenyl functional groups also adsorbs the phenyl-containing food-grade antioxidant through the π-π stacking effect, achieving the loading of the phenyl-containing food-grade antioxidant, and finally in the molten state, the long-chain alkyl groups rich in the diatomite and the non-polar long-chain alkane structure with a high similarity in chemical structure to the linear low-density polyethylene resin molecular chain penetrate and diffuse into the amorphous region of the linear low-density polyethylene resin through thermal motion, and are intertwined and tightly combined with the linear low-density polyethylene resin molecular chain, achieving the physical anchoring effect, and an antioxidant active polyethylene masterbatch is prepared;

[0032] The antioxidant active polyethylene masterbatch is used as a functional modification raw material of polyethylene resin, and is introduced into a three-layer co-extrusion PE film to prepare a plastic cup heat-sealing composite film with an antioxidant active sealing function through a three-layer co-extrusion blown film forming process.

[0033] The experimental results prove that the prepared film product of the application almost does not release the loaded antioxidant under the condition of no heat sealing, while the heat sealing process can trigger the release of the antioxidant, and accordingly the prepared film product of the application can provide antioxidant protection for the cup-packed fresh-pressed juice product after heat sealing; and the heat sealing performance of the prepared film product of the application meets the technical requirements of GB / T 281176-2011 “Multilayer co-extrusion film, bag for food packaging”. DETAILED DESCRIPTION

[0034] Example 1:

[0035] The synthesis mechanism of the long-chain alkyl phenyl silane coupling agent is as follows:

[0036] Based on the Friedel-Crafts alkylation reaction mechanism, under the catalysis of Lewis acid, octa-phenyl-POSS is used as raw material, first, electrophilic substitution reaction occurs between the phenyl functional groups and the alkyl functional groups of long straight-chain alpha-olefin, then electrophilic substitution reaction occurs between the remaining phenyl functional groups and the alkyl functional groups of vinyltrimethoxysilane, and the molar ratio of octa-phenyl-POSS, long straight-chain alpha-olefin and vinyltrimethoxysilane participating in the reaction is controlled to be 1:0.97:0.99, and the long-chain alkyl phenyl silane coupling agent is synthesized;

[0037] The long straight chain alpha-olefin is one of 1-tetradecene, 1-hexadecene and 1-octadecene, and the chemical structure general formula of the long chain alkyl phenyl silane coupling agent synthesized according to the long straight chain alpha-olefin is:

[0038] ;

[0039] The long straight chain alpha-olefin in the embodiment is 1-octadecene, and the long chain alkyl phenyl silane coupling agent synthesized according to the long straight chain alpha-olefin is octadecyl phenyl silane coupling agent, and the chemical structure formula is:

[0040] ;

[0041] The Lewis acid is one of anhydrous AlCl3 and anhydrous FeCl3, and the Lewis acid in the embodiment is anhydrous AlCl3;

[0042] The specific experimental steps of the octadecyl phenyl silane coupling agent are as follows:

[0043] 1g of octaphenyl-POSS, 0.32mL of 1-octadecene and 0.26g of anhydrous AlCl3 are added into 40mL of dichloroethane, and then magnetically stirred for 20min under nitrogen protection, the temperature is adjusted to 40℃, and then incubated for 8h, and then 0.15mL of vinyl trimethoxysilane is added, the temperature is increased to 75℃, and then incubated for 10h, and then cooled to room temperature, and then filtered under reduced pressure, and then the crude product is collected, and then the crude product is washed with deionized water and methanol, and then the crude product is further extracted with methanol and dichloroethane by Soxhlet extraction, and then purified for 12h respectively, and then the product is dried in a vacuum drying box at 70℃ for 12h, and then octadecyl phenyl silane coupling agent is obtained;

[0044] The hydrogen spectrum characterization result of the octadecyl phenyl silane coupling agent is as follows:

[0045] 1 H NMR (400MHz, CDCl3, δ, ppm): 0.88-0.90 (t, 3H), 0.95-1.10 (m, 2H), 1.27-1.35 (m, 30H), 1.58-1.64 (m, 2H), 2.53-2.66 (m, 4H), 3.57 (s, 9H), 7.10-7.15 (m, 4H), 7.26-7.34 (m, 18H), 7.43-7.45 (d, 4H), 7.50-7.53 (m, 12H);

[0046] The specific experimental steps of the long chain alkyl phenyl functionalized diatomite are as follows:

[0047] 2 g diatomite with 200 mesh standard sieve was added into 40 mL deionized water and 40 mL anhydrous ethanol mixed solution, ultrasonic dispersion was carried out for 20 min, 0.2 g octadecyl phenyl silane coupling agent was added, heated to 50℃, stirred at 300 r / min, stirred for 1 h, suction filtered, washed with deionized water, placed in 80℃ drying oven for drying for 8 h, after drying, sieved again with 200 mesh standard sieve, long chain alkyl phenyl functionalized diatomite was obtained;

[0048] The specific experimental steps of long chain alkylated antioxidant diatomite were as follows:

[0049] 2 g long chain alkyl phenyl functionalized diatomite and 4.5 mL carvacrol were added into a suction filter bottle, mixed at 300 r / min stirring rate for 10 min, then vacuum suction filtration was carried out, the operation was repeated for 10 times, each time for 30 s, after suction filtration, the mixture was transferred into a centrifuge tube, centrifuged at 5000 r / min for 5 min, the supernatant was recovered into a suction filter bottle, the operation was repeated, centrifuged for the second time, finally placed in a 60℃ vacuum drying oven for drying for 10 h, long chain alkylated antioxidant diatomite was obtained;

[0050] The specific experimental steps of antioxidant active polyethylene masterbatch were as follows:

[0051] 9 parts by weight of linear low density polyethylene (model 7042) and 1 part by weight of long chain alkylated antioxidant diatomite were uniformly mixed in a high-speed mixer, then added into a twin-screw extruder hopper, melt extrusion granulation was carried out, antioxidant active polyethylene masterbatch was prepared;

[0052] The process parameters of the twin-screw extruder were set as follows: the heating section temperature was 150℃, the mixing section temperature was 155℃, the extrusion section temperature was 160℃, and the screw rotation speed was 30 r / min.

[0053] Example two:

[0054] A plastic cup heat sealing composite film I with antioxidant active sealing function, the product structure was as follows: the layers were arranged in sequence:

[0055] Outer layer: the formula was 70wt% high density polyethylene resin (model DGDX-6095) and 30wt% linear low density polyethylene resin (model 7042), and the amount was 25 parts by weight;

[0056] Middle layer: the formula was 80wt% high density polyethylene resin (model DGDX-6095) and 20wt% linear low density polyethylene resin (model 7042), and the amount was 50 parts by weight;

[0057] Inner layer: the formula was 80wt% low density polyethylene resin (model Q281) and 20wt% antioxidant active polyethylene masterbatch, and the amount was 25 parts by weight;

[0058] The preparation method of the composite film I for heat sealing of plastic cups comprises the following specific steps:

[0059] The raw materials of each layer are respectively put into the hoppers corresponding to the three single-screw extruders in the three-layer co-extrusion film blowing machine set according to the formula amount, the raw materials are uniformly stirred and mixed, the molten resins are converged at the machine head through a flow divider, and then the composite film I with a thickness of 60 μm is prepared through extrusion blowing, cooling and winding.

[0060] The temperature of each zone of the single-screw extruder corresponding to the outer layer is: zone 1, 120℃; zone 2, 150℃; zone 3, 175℃; the flow channel temperature is 165℃; and the screw rotation speed is 30 r / min.

[0061] The temperature of each zone of the single-screw extruder corresponding to the middle layer is: zone 1, 120℃; zone 2, 155℃; zone 3, 175℃; the flow channel temperature is 165℃; and the screw rotation speed is 35 r / min.

[0062] The temperature of each zone of the single-screw extruder corresponding to the inner layer is: zone 1, 110℃; zone 2, 145℃; zone 3, 160℃; the flow channel temperature is 155℃; and the screw rotation speed is 25 r / min.

[0063] The conditions of the extrusion blowing process are: the pulling speed is 5 m / min, the diameter of the film blowing machine die is 60 mm, and the blowing ratio is 2.4.

[0064] Example Three:

[0065] The composite film II is prepared, and the difference between the preparation method of the composite film II and the preparation method of the composite film I is only that the inner layer is prepared from 70wt% low-density polyethylene resin (model Q281) and 30wt% antioxidant active polyethylene master batch, and the amount is 25 parts by weight.

[0066] Example Four:

[0067] The composite film III is prepared, and the difference between the preparation method of the composite film III and the preparation method of the composite film I is only that the inner layer is prepared from 60wt% low-density polyethylene resin (model Q281) and 40wt% antioxidant active polyethylene master batch, and the amount is 25 parts by weight.

[0068] Performance test:

[0069] I. Antioxidant experiment:

[0070] Antioxidant experiment of the composite film produced on the same day: The composite film was sealed with a PP plastic cup using an HSG-C type heat sealer. The heat sealing temperature was 160℃, the heat sealing pressure was 0.1MPa, and the heat sealing time was 1s. 0.5g of the heat-sealed composite film was weighed, cut into small pieces, and added to 10mL of anhydrous ethanol for soaking. It was then stored in a 37℃ shaking incubator in the dark and sealed. 7.89mg of DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) was weighed and dissolved in 100mL of anhydrous ethanol. The solution was then transferred to a 200mL volumetric flask and diluted to volume to obtain a 0.1mmol / L DPPH ethanol solution. The supernatant of 1mL of the composite film anhydrous ethanol solution was added to 1mL of 0... The DPPH ethanol solution was mixed thoroughly in 0.1 mmol / L and allowed to stand in the dark for 1 hour. The absorbance at 517 nm was then measured using a UV spectrophotometer. The formula for the DPPH free radical scavenging rate is: Free radical scavenging rate (%) = (A0 - A1 / A0) × 100%, where A0 is the absorbance of the DPPH ethanol solution and A1 is the absorbance of the DPPH ethanol solution after adding the supernatant. The antioxidant performance of the heat-sealed composite film was evaluated using the DPPH free radical scavenging rate method. The DPPH ethanol solution was a purple solution with the highest absorbance at 517 nm. When the antioxidant reacted with DPPH, the purple solution would fade and the absorbance would decrease.

[0071] Antioxidant test of composite film placed indoors at room temperature for 90 days: Following the antioxidant test method for composite film produced on the same day, an antioxidant test was conducted on the composite film placed indoors at room temperature for 90 days. The test results are recorded in Table 1:

[0072] Table 1. Experimental results of the antioxidant properties of the composite membrane.

[0073] Product No. Radical scavenging rate (%) at day 0 Radical scavenging rate (%) at day 90 Composite film I 83.9 83.8 Composite film II 88.0 88.1 Composite film III 90.1 89.5

[0074] II. The heat-sealing performance of the composite film was tested according to QB / T 2358-1998 "Test Method for Heat Seal Strength of Plastic Film Packaging Bags". The composite film was sealed with a PP plastic cup using an HSG-C type heat sealer. The heat-sealing temperature was 160℃, the heat-sealing pressure was 0.1MPa, the heat-sealing time was 1s, the distance between the clamps was 50mm, and the test speed was 300mm / min. The peel strength of the composite film was tested according to GB / T 8808-1988 "Peel Strength Test Method for Flexible Composite Plastic Materials". The sample size was 15mm and the length was 200mm. The test speed was 300mm / min. The test results are recorded in Table 2.

[0075] Table 2. Experimental results of heat-sealing performance of composite films

[0076] Product No. Heat seal strength (N / 15 mm) Peeling strength (N / 15 mm) Composite film I 16.3 7.2 Composite film II 15.1 8.1 Composite film III 13.9 7.7

[0077] The heat sealing strength of the composite film prepared by the application meets the technical requirement of GB / T 281176-2011 "Multilayer Co-extrusion Film and Bag for Food Packaging" that the heat sealing strength is greater than or equal to 10 N / 15 mm (material thickness R, 0.051 mm≤R<0.1 mm);

[0078] And the peel strength also meets the technical requirement of GB / T 281176-2011 "Multilayer Co-extrusion Film and Bag for Food Packaging" that the peel strength is greater than or equal to 4 N / 15 mm (material thickness R, 0.051 mm≤R<0.1 mm).

Claims

1. A composite film for heat-sealing plastic cups, characterized in that, The product structure of the composite membrane is as follows: Outer layer: The formula consists of 60-80 wt% high-density polyethylene resin and 20-40 wt% linear low-density polyethylene resin, with a dosage of 20-30 parts by weight; Intermediate layer: The formulation consists of 70-90 wt% high-density polyethylene resin and 10-30 wt% linear low-density polyethylene resin, with a dosage of 40-60 parts by weight; Inner layer: The formula consists of 60-80wt% low-density polyethylene resin and 20-40wt% antioxidant active polyethylene masterbatch, with a dosage of 20-30 parts by weight; The preparation method of the antioxidant active polyethylene masterbatch is as follows: Based on the silanol condensation reaction mechanism, long-chain alkylphenyl silane coupling agents were modified onto silanol-rich diatomaceous earth to prepare long-chain alkylphenyl functionalized diatomaceous earth. Long-chain alkylphenyl functionalized diatomaceous earth physically adsorbs phenyl-containing food-grade antioxidants through its rich internal pores and adsorbs the antioxidants through π-π stacking interactions with the antioxidants on its rich surface phenyl content, thus producing long-chain alkylated antioxidant diatomaceous earth. During the melt blending process, the long-chain alkyl groups on the surface of the long-chain alkylated antioxidant diatomaceous earth diffuse and entangle with the molecular chains of linear low-density polyethylene resin, thereby achieving uniform dispersion and firm bonding of diatomaceous earth in the linear low-density polyethylene resin matrix and obtaining antioxidant active polyethylene masterbatch. The general chemical structural formula of the long-chain alkylphenylsilane coupling agent is: 。 2. The composite film for heat-sealing plastic cups according to claim 1, characterized in that, The mass ratio of diatomite to long-chain alkylphenyl silane coupling agent in the long-chain alkylphenyl functionalized diatomite is 1:0.075-0.

15.

3. The composite film for heat-sealing plastic cups according to claim 1, characterized in that, The mass ratio of long-chain alkylphenyl functionalized diatomaceous earth to phenyl-containing food-grade antioxidant in the long-chain alkylphenyl antioxidant diatomaceous earth is 1:1.5-2.

5.

4. The composite film for heat-sealing plastic cups according to claim 1, characterized in that, The mass ratio of linear low-density polyethylene resin to long-chain alkylated antioxidant diatomaceous earth in the antioxidant active polyethylene masterbatch is 1:0.05-0.

15.

5. The composite film for heat-sealing plastic cups according to claim 1, characterized in that, The phenyl-containing food-grade antioxidant is one of carvacrol and α-tocopherol.

6. The composite film for heat-sealing plastic cups according to claim 1, characterized in that, The thickness of the composite membrane is 30-80 μm.

7. The method for preparing the composite film for heat sealing of plastic cups according to any one of claims 1-6, characterized in that, Includes the following steps: According to the formula, the raw materials of each layer are fed into the hoppers of the three single-screw extruders of the three-layer co-extrusion film blow molding unit. The molten resin is combined at the die head through the distributor, extruded and blow molded through the die head, cooled, and wound up to obtain a composite film. The temperatures of each zone of the single-screw extruder corresponding to the outer layer are: Zone 1 115-125℃, Zone 2 145-160℃, Zone 3 170-180℃, flow channel temperature 160-170℃, and screw speed 25-35r / min. The temperatures of each zone of the single-screw extruder corresponding to the intermediate layer are: Zone 1 115-125℃, Zone 2 150-165℃, Zone 3 170-180℃, the flow channel temperature is 160-170℃, and the screw speed is 30-40r / min. The temperatures of each zone of the single-screw extruder corresponding to the inner layer are: Zone 1 105-115℃, Zone 2 140-155℃, Zone 3 155-165℃, the flow channel temperature is 145-155℃, and the screw speed is 20-30 r / min.

8. The method for preparing a composite film for heat sealing of a plastic cup according to claim 7, characterized in that, The preparation method of the long-chain alkylphenylsilane coupling agent is as follows: Based on the Friedel-Crafts alkylation mechanism, under the catalysis of Lewis acids, using octaphenyl-POSS as a starting material, a long-chain alkylphenylsilane coupling agent is synthesized by first undergoing an electrophilic substitution reaction between the phenyl functional group and the alkenyl functional group of a long-chain α-olefin, and then undergoing an electrophilic substitution reaction between the remaining phenyl functional group and the alkenyl functional group of vinyltrimethoxysilane. The molar ratio of octaphenyl-POSS, long-chain α-olefin, and vinyltrimethoxysilane participating in the reaction is controlled to be 1:0.95-0.99:0.95-0.

99. The long-chain α-olefin is one of 1-tetradecene, 1-hexadecene, and 1-octadecene.

9. The method for preparing a composite film for heat sealing of a plastic cup according to claim 8, characterized in that, The Lewis acid is one of anhydrous AlCl3 or anhydrous FeCl3.

10. The application of the composite film for heat-sealing plastic cups according to any one of claims 1-6, characterized in that, The composite film triggers the release of antioxidants into the sealed space of the plastic cup through a heat-sealing process, providing antioxidant protection for the cup-packaged fresh juice product.

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