A multilayer anti-fog heat-shrinkable polyolefin sealing film and a method for preparing the same

Abstract

The application is suitable for the technical field of film production, and provides a multilayer anti-fog heat-shrinkable polyolefin sealing film and a preparation method thereof.The sealing film comprises a multilayer co-extrusion structure: a contact layer comprising a metallocene polyolefin, modified cyclodextrin-poly ionic liquid and dynamic borate anti-fog agent; a functional layer comprising modified diatomite and nano calcium carbonate; and a protective layer comprising nano cellulose aerogel and metal organic framework silver-loaded particles.The contact layer of the sealing film adopts modified cyclodextrin-poly ionic liquid and dynamic borate anti-fog agent to realize molecular lock anti-migration and humidity response self-repair.The functional layer adopts micron-level protrusions on the surface of modified diatomite to destroy mirror reflection, reduce gloss, fill diatomite pores with nano calcium carbonate to reduce internal light scattering, reduce haze and improve light transmittance.The protective layer adopts nano cellulose aerogel and metal organic framework silver-loaded particles to construct super-hydrophilic micro-channels and antibacterial and mildew-proof functions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of film production, and particularly relates to a multilayer anti-fog heat-shrinkable polyolefin sealing film and a preparation method thereof. BACKGROUND

[0002] The heat-shrinkable polyolefin sealing film is widely used in the field of food packaging, and its anti-fog performance directly affects the commodity display effect. The current mainstream technology has the following problems:

[0003] Severe migration of anti-fog agent: the traditional migration type anti-fog agent (such as glycerol monostearate) realizes anti-fog by surface precipitation, but has high migration rate, resulting in short effective period.

[0004] Optical performance contradiction: although the addition of talc powder in the matt layer reduces the gloss, a large number of light scattering centers are introduced, the haze is as high as 50-60%, and the light transmittance is low. SUMMARY

[0005] The application provides a multilayer anti-fog heat-shrinkable polyolefin sealing film, and aims to solve the above problems.

[0006] The application is implemented as follows: a multilayer anti-fog heat-shrinkable polyolefin sealing film comprises a multilayer co-extrusion structure:

[0007] A contact layer comprising a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid and a dynamic borate anti-fog agent;

[0008] A functional layer comprising modified diatomite and nano calcium carbonate;

[0009] A protective layer comprising nano cellulose aerogel and metal organic framework silver-loaded particles.

[0010] Preferably, the contact layer comprises, by weight parts: 65-75 parts of metallocene linear low-density polyethylene, 5-7 parts of modified cyclodextrin-poly ionic liquid, 2-4 parts of dynamic borate anti-fog agent, and 1-2 parts of nano silicon dioxide.

[0011] Preferably, the functional layer comprises, by weight parts: 25-35 parts of polypropylene, 45-55 parts of low-density polyethylene, 10-20 parts of modified diatomite, 8-12 parts of nano calcium carbonate, and 0.5-1 part of erucamide.

[0012] Preferably, the protective layer comprises, by weight parts: 60-70 parts of low-density polyethylene, 15-25 parts of ethylene-vinyl acetate copolymer, 7-9 parts of nano cellulose aerogel, and 1-3 parts of metal organic framework silver-loaded particles.

[0013] Preferably, the raw material of the contact layer comprises 0.3-0.7 parts of aluminum acetylacetonate and 0.1-0.3 parts of sodium pyrophosphate, which is used for improving the thermal stability of the dynamic borate anti-fog agent.

[0014] The application also provides a preparation method of the multi-layer anti-fog heat-shrinkable polyolefin sealing film.

[0015] (1) Raw material preparation and mixing: preparing raw materials for each layer according to the formula;

[0016] (2) Melt co-extrusion: multi-layer co-extrusion, and the temperature control of each layer is as follows:

[0017] Temperature zone of the contact layer extruder: feeding zone 150±2℃→melting zone 165±2℃→homogenizing zone 170±2℃;

[0018] Temperature zone of the functional layer extruder: feeding zone 155±2℃→melting zone 195±2℃→homogenizing zone 185±2℃;

[0019] Temperature zone of the protective layer extruder: feeding zone 145±2℃→melting zone 160±2℃→homogenizing zone 175±2℃;

[0020] Die connecting body temperature: 170±2℃;

[0021] (3) Supercritical CO2 quenching: injecting supercritical CO2 (temperature 30-32℃, pressure 7.2-7.6MPa) in the sharp cooling section; reducing the crystallinity and increasing the transverse heat shrinkage rate.

[0022] (4) Asynchronous bidirectional gradient stretching: longitudinal 1.4-1.6 times pre-stretching (85-95℃), infrared gradient heating to 110-115℃, and transverse 3.0-3.4 times secondary stretching;

[0023] (5) Alternating electric field aging treatment: frequency 20-100Hz, field strength 4-6kV / cm, and time 20-40min; using variable frequency alternating electric field to promote molecular chain relaxation, reduce residual stress, and make the heat shrinkage rate more stable.

[0024] (6) Winding and slitting.

[0025] Preferably, the preparation steps of the modified cyclodextrin-polyionic liquid are as follows:

[0026] Dissolving β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:4-6), adding 4-vinylbenzyl chloride (molar ratio of β-cyclodextrin to 4-vinylbenzyl chloride is 1:0.2-0.4), and reacting at 68-72℃ for 11.5-12.5h;

[0027] Pouring the reaction solution into ice ethanol to precipitate, and filtering to obtain vinyl cyclodextrin;

[0028] Vinyl cyclodextrin and 1-vinyl-3-ethylimidazolium bromide were mixed at a molar ratio of 1:4-6, 0.1-0.2 mol% azobisisobutyronitrile was added, and polymerization was carried out at 59-61°C under nitrogen protection for 18-20h;

[0029] Ethanol was washed three times and dried at 60°C under vacuum.

[0030] By β-cyclodextrin cavity inclusion of anti-fog agent molecules, polyionic liquid is anchored on the polyolefin chain through electrostatic interaction, locking anti-fog agent, reducing migration rate.

[0031] Preferably, the preparation steps of the dynamic borate anti-fog agent are as follows:

[0032] 4-vinylphenylboronic acid was dissolved in tetrahydrofuran (mass ratio 1:3-5), sorbitol (molar ratio of 4-vinylphenylboronic acid to sorbitol 1:0.3-0.5) and 0.5wt% p-toluenesulfonic acid were added;

[0033] Reflux at 78-82°C for 6-8h, remove tetrahydrofuran by rotary evaporation;

[0034] Washed with acetone three times, a transparent viscous liquid was obtained.

[0035] By forming a humidity-responsive covalent bond between phenylboronic acid and sorbitol, the surface micro-cracks are automatically repaired when the environmental humidity is high, and the anti-fogging life is improved.

[0036] Preferably, the preparation steps of the modified diatomite are as follows:

[0037] Mix diatomite with 10-15wt% hydrochloric acid at a mass ratio of 1:5-8, stir in a microwave reactor at 75-85°C for 40-50min (power 700-800W), centrifugal separation, and wash with deionized water until neutral to obtain expanded diatomite;

[0038] Graded by weight, take 90-110 parts of expanded diatomite, add 4-6 times the weight of anhydrous ethanol, ultrasonic treatment (40-50kHz, 30-40min), add titanate coupling agent, reflux at 70-78°C for 1.5-2h;

[0039] Dropwise addition of stearic acid ethanol solution (concentration 4-6wt%), continue to react for 1h, suction filtration, and vacuum drying at 60-70°C for 12h;

[0040] Grind in a ball mill with zirconia balls (Φ3mm, ball to material ratio 5:1, rotation speed 250rpm, time 40-50min) to obtain modified diatomite.

[0041] By modifying the micron-level protrusions on the surface of diatomite, mirror reflection is destroyed, gloss is reduced, nano-calcium carbonate fills the pores of diatomite, internal light scattering is reduced, haze is reduced, and light transmittance is improved.

[0042] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0043] Disperse bleached wood pulp in water (solid content 10-15wt%), add TEMPO (wood pulp: TEMPO = 50-55: 1 w / w) and sodium bromide (wood pulp: NaBr = 5: 1 w / w);

[0044] Drop 8-12wt% sodium hypochlorite solution to pH = 10.0 ± 0.2, react for 5-6h;

[0045] Stop the reaction with 0.5M hydrochloric acid, centrifugal wash to get carboxylated nanocellulose;

[0046] Carboxylated nanocellulose reacts with sodium sulfite (CNF-COOH: Na2SO3 = 1: 0.08-0.12 w / w) at 79-81℃ for 2-3h;

[0047] Freeze-drying (-55~-45℃, 8-12Pa), spray 0.2-0.4% triethyl citrate ethanol solution, cross-linking and reinforcement, heat treatment at 75-85℃ for 25-35min.

[0048] Form super-hydrophilic micro-channel network through nanocellulose aerogel, instantaneous anti-fogging by water guide.

[0049] Preferably, the preparation steps of the metal organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0050] Dissolve 2-methylimidazole in methanol (concentration 2-3wt%), add silver nitrate (2-methylimidazole: AgNO3 = 4-6: 1 w / w), stir for 25-35min;

[0051] Drop methanol solution containing zinc nitrate hexahydrate (2-methylimidazole: zinc nitrate hexahydrate = 2-3: 1 w / w), react at 22-26℃ for 18-24h;

[0052] Centrifugal (7000-9000rpm, 10-15min), wash with methanol three times, dry at 60℃;

[0053] Put into stearic acid / ethanol solution (concentration 2wt%) for immersion (solid-liquid ratio 1:10), oscillate at 55-65℃ for 2h, vacuum drying, stearic acid coating forms a monolayer protection skeleton.

[0054] Control silver ion release through ZIF-8, inhibit microbial growth (bacteriostatic rate >99.9%), solve the biological fogging after long-term use.

[0055] Preferably, the nanocellulose aerogel and the metal organic framework silver-loaded particles are compounded by freeze electron beam irradiation:

[0056] The nanocellulose aerogel is immersed in an EVA / toluene solution containing 4-6wt% metal organic framework silver-loaded particles;

[0057] Frozen in liquid nitrogen to-196℃, 9-11kGy electron beam irradiation;

[0058] After thawing at room temperature, drying forms an interpenetrating network structure.

[0059] Compared with the prior art, the embodiments of the application have the following beneficial effects:

[0060] The contact layer of the multi-layer anti-fog heat-shrinkable polyolefin sealing film provided by the application adopts modified cyclodextrin-polyionic liquid and dynamic borate ester anti-fog agent, realizes molecular lock anti-migration and humidity response self-repair; the functional layer adopts micron-level protrusions on the surface of modified diatomite, destroys mirror reflection, reduces gloss, nano calcium carbonate fills diatomite pores, reduces internal light scattering, reduces haze, and improves light transmittance; the protective layer adopts nanocellulose aerogel and metal organic framework silver-loaded particles, constructs super-hydrophilic micro-channels and antibacterial and mildew-proof functions. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The application provides a preparation method flow chart of a multi-layer anti-fog heat-shrinkable polyolefin sealing film. DETAILED DESCRIPTION

[0062] Unless otherwise defined, 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 application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; the description and the drawings are to be regarded as illustrative in nature and are not intended to limit the application; the terminology used in the description and the claims of the present application and the above description of drawings includes the terms "comprising", "having" and the like, which are to be interpreted open, as meaning "including, but not limited to". The terms "first", "second", and the like, as used in the description and the claims of the present application and the above description of drawings, are used to identify different objects, not to describe a particular sequential order.

[0063] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0064] Embodiment 1

[0065] The multilayer anti-fog heat-shrinkable polyolefin sealing film provided by the embodiment of the application comprises a multilayer co-extrusion structure:

[0066] a contact layer comprising a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid, and a dynamic borate anti-fog agent;

[0067] a functional layer comprising modified diatomite and nano calcium carbonate;

[0068] a protective layer comprising nano-cellulose aerogel and metal-organic framework silver-loaded particles.

[0069] In the embodiment, the contact layer comprises, by weight parts, 65 parts of metallocene linear low-density polyethylene, 5 parts of modified cyclodextrin-poly ionic liquid, 2 parts of dynamic borate anti-fog agent, 1 part of nano silicon dioxide, 0.3 parts of acetylacetone aluminum, and 0.1 parts of sodium pyrophosphate.

[0070] The functional layer comprises, by weight parts, 25 parts of polypropylene, 45 parts of low-density polyethylene, 10 parts of modified diatomite, 8 parts of nano calcium carbonate, and 0.5 parts of erucamide.

[0071] The protective layer comprises, by weight parts, 60 parts of low-density polyethylene, 15 parts of ethylene-vinyl acetate copolymer, 7 parts of nano-cellulose aerogel, and 1 part of metal-organic framework silver-loaded particles.

[0072] The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment, as shown in Figure 1 , comprises the following steps:

[0073] (1) raw material preparation and mixing: preparing raw materials for each layer according to the formula;

[0074] (2) melt co-extrusion: multilayer co-extrusion, and the temperature control of each layer is as follows:

[0075] The temperature zone of the contact layer extruder: feeding zone 148℃→melting zone 163℃→homogenization zone 168℃;

[0076] The temperature zone of the functional layer extruder: feeding zone 153℃→melting zone 193℃→homogenization zone 183℃;

[0077] The temperature zone of the protective layer extruder: feeding zone 143℃→melting zone 158℃→homogenization zone 173℃;

[0078] The temperature of the die connecting body: 168℃;

[0079] (3) supercritical CO2 quenching: injecting supercritical CO2 (temperature 30℃, pressure 7.2MPa) in the sharp cooling section;

[0080] (4) asynchronous bidirectional gradient stretching: longitudinal 1.4 times pre-stretching (85℃), infrared gradient heating to 110℃, and transverse 3.0 times secondary stretching;

[0081] (5) Alternating electric field aging treatment: frequency 20-100 Hz, field strength 4-6 kV / cm, time 20 min;

[0082] (6) Winding and slitting.

[0083] The preparation steps of the modified cyclodextrin-polyion liquid are as follows:

[0084] Dissolve β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:4), add 4-vinyl benzyl chloride (molar ratio of β-cyclodextrin to 4-vinyl benzyl chloride is 1:0.2), and react at 68°C for 11.5 h;

[0085] Pour the reaction solution into ice ethanol for precipitation, and filter to obtain vinyl cyclodextrin;

[0086] Mix vinyl cyclodextrin and 1-vinyl-3-ethyl imidazole bromide salt at a molar ratio of 1:4, add 0.1 mol% azobisisobutyronitrile, and polymerize at 59°C under nitrogen protection for 18 h;

[0087] Wash with ethanol three times, and dry at 60°C under vacuum.

[0088] Further, the preparation steps of the dynamic borate antifogging agent are as follows:

[0089] Dissolve 4-vinyl phenylboronic acid in tetrahydrofuran (mass ratio 1:3), add sorbitol (molar ratio of 4-vinyl phenylboronic acid to sorbitol is 1:0.3), and 0.5 wt% p-toluenesulfonic acid;

[0090] Reflux at 78°C for 6 h, and remove tetrahydrofuran by rotary evaporation;

[0091] Wash with acetone three times to obtain a transparent viscous liquid.

[0092] Further, the preparation steps of the modified diatomite are as follows:

[0093] Mix diatomite and 10 wt% hydrochloric acid at a mass ratio of 1:5, and stir in a microwave reaction kettle at 75°C for 40 min (power 700 W), centrifugal separation, and wash with deionized water until neutral to obtain expanded diatomite;

[0094] Graded by weight, take 90 parts of expanded diatomite, add 4 times the weight of anhydrous ethanol, ultrasonic treatment (40 kHz, 30 min), add a titanate coupling agent, and reflux at 70°C for 1.5 h;

[0095] Drop ethanol solution of stearic acid (concentration 4 wt%), continue to react for 1 h, suction filtration, and dry at 60°C under vacuum for 12 h;

[0096] The modified diatomite was obtained by grinding in a ball mill with zirconium oxide balls (Φ3 mm, ball-to-material ratio 5:1, rotation speed 250 rpm, time 40 min).

[0097] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0098] The bleached wood pulp was dispersed in water (solid content 10 wt%), TEMPO (wood pulp: TEMPO = 50:1 w / w) and sodium bromide (wood pulp: NaBr = 5:1 w / w) were added;

[0099] 8 wt% sodium hypochlorite solution was added dropwise to pH = 10.0 ± 0.2, and the reaction was carried out for 5 h;

[0100] The reaction was terminated with 0.5 M hydrochloric acid, and the carboxylated nanocellulose was washed by centrifugation;

[0101] The carboxylated nanocellulose was reacted with sodium sulfite (CNF-COOH: Na2SO3 = 1:0.08 w / w) at 79-81 °C for 2 h;

[0102] Freeze-drying (-55 °C, 8 Pa), spraying 0.2% triethyl citrate ethanol solution, cross-linking and reinforcement, 75 °C heat treatment for 25 min.

[0103] In a specific implementation, the preparation steps of the metal organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0104] 2-methylimidazole was dissolved in methanol (concentration 2 wt%), silver nitrate was added (2-methylimidazole: AgNO3 = 4:1 w / w), and stirring was carried out for 25-35 min;

[0105] A methanol solution containing zinc nitrate hexahydrate (2-methylimidazole: zinc nitrate hexahydrate = 2:1 w / w) was added dropwise, and the reaction was carried out at 22 °C for 18 h;

[0106] Centrifugation (7000 rpm, 10 min), methanol washing three times, and drying at 60 °C;

[0107] Immersion in a stearic acid / ethanol solution (concentration 2 wt%) (solid-liquid ratio 1:10), 55 °C oscillation for 2 h, vacuum drying, stearic acid coating to form a monolayer-protected skeleton.

[0108] Further, the nanocellulose aerogel and the metal organic framework silver-loaded particles are compounded by freeze electron beam irradiation:

[0109] The nanocellulose aerogel was immersed in an EVA / toluene solution containing 4 wt% metal organic framework silver-loaded particles;

[0110] Liquid nitrogen freezing to -196 °C, 9 kGy electron beam irradiation;

[0111] Drying after thawing at room temperature, forming an interpenetrating network structure.

[0112] Example 2

[0113] The embodiment of the application provides a multilayer anti-fog heat-shrinkable polyolefin sealing film, comprising a multilayer co-extrusion structure:

[0114] The contact layer comprises a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid and a dynamic borate anti-fog agent.

[0115] The functional layer comprises modified diatomite and nano calcium carbonate.

[0116] The protective layer comprises nano cellulose aerogel and metal organic framework silver-loaded particles.

[0117] In the embodiment, the contact layer comprises, by weight parts, 68 parts of metallocene linear low-density polyethylene, 5.5 parts of modified cyclodextrin-poly ionic liquid, 2.5 parts of dynamic borate anti-fog agent, 1.2 parts of nano silicon dioxide, 0.4 parts of acetylacetone aluminum and 0.15 parts of sodium pyrophosphate.

[0118] The functional layer comprises, by weight parts, 27 parts of polypropylene, 48 parts of low-density polyethylene, 12 parts of modified diatomite, 9 parts of nano calcium carbonate and 0.6 parts of erucamide.

[0119] The protective layer comprises, by weight parts, 63 parts of low-density polyethylene, 17 parts of ethylene-vinyl acetate copolymer, 7.5 parts of nano cellulose aerogel and 1.5 parts of metal organic framework silver-loaded particles.

[0120] The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment is shown in the following steps. Figure 1 The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment is shown in the following steps.

[0121] (1) Raw material preparation and mixing: preparing raw materials of each layer according to the formula;

[0122] (2) Melt co-extrusion: multilayer co-extrusion, and the temperature control of each layer is as follows:

[0123] The temperature zone of the contact layer extruder is: feeding zone 148 DEG C -> melting zone 163 DEG C -> homogenizing zone 168 DEG C.

[0124] The temperature zone of the functional layer extruder is: feeding zone 153 DEG C -> melting zone 193 DEG C -> homogenizing zone 183 DEG C.

[0125] The temperature zone of the protective layer extruder is: feeding zone 143 DEG C -> melting zone 158 DEG C -> homogenizing zone 173 DEG C.

[0126] The temperature of the die connecting body is 168 DEG C.

[0127] (3) supercritical CO2 quenching: injecting supercritical CO2 (temperature 30℃, pressure 7.2MPa) in the sharp cooling section;

[0128] (4) asynchronous bidirectional gradient stretching: longitudinal 1.4 times pre-stretching (85℃), infrared gradient heating to 110℃, transverse 3.0 times secondary stretching;

[0129] (5) alternating electric field aging treatment: frequency 20-100Hz, field strength 4-6kV / cm, time 20min;

[0130] (6) winding and slitting.

[0131] The preparation steps of the modified cyclodextrin-polyion liquid are as follows:

[0132] Dissolve β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:4), add 4-vinyl benzyl chloride (molar ratio of β-cyclodextrin to 4-vinyl benzyl chloride is 1:0.2), and react at 68℃ for 11.5h;

[0133] Pour the reaction solution into ice ethanol for precipitation, and filter to obtain vinyl cyclodextrin;

[0134] Mix vinyl cyclodextrin and 1-vinyl-3-ethyl imidazole bromide salt according to a molar ratio of 1:4, add 0.1mol% azobisisobutyronitrile, and polymerize at 59℃ under nitrogen protection for 18h;

[0135] Wash with ethanol three times, and dry at 60℃ under vacuum.

[0136] Further, the preparation steps of the dynamic borate antifogging agent are as follows:

[0137] Dissolve 4-vinyl phenylboronic acid in tetrahydrofuran (mass ratio 1:3), add sorbitol (molar ratio of 4-vinyl phenylboronic acid to sorbitol is 1:0.3) and 0.5wt% p-toluenesulfonic acid;

[0138] Reflux at 78℃ for 6h, and remove tetrahydrofuran by rotary evaporation;

[0139] Wash with acetone three times to obtain a transparent viscous liquid.

[0140] Still further, the preparation steps of the modified diatomite are as follows:

[0141] Mix diatomite and 10wt% hydrochloric acid according to a mass ratio of 1:5, and react at 75℃ in a microwave reaction kettle for 40min (power 700W), centrifugal separation, and wash with deionized water until neutral to obtain expanded diatomite;

[0142] Graded by weight, take 90 parts of expanded diatomite, add 4 times the weight of anhydrous ethanol, ultrasonic treatment (40 kHz, 30 min), add titanium ester coupling agent, 70℃ backflow 1.5h;

[0143] Drop in the ethanol solution of stearic acid (concentration 4wt%), continue to react for 1h, suction filtration, 60℃ vacuum drying 12h;

[0144] Grind in the ball mill with zirconium oxide balls (Φ3mm, ball to material ratio 5:1, rotation speed 250rpm, time 40min) to obtain modified diatomite.

[0145] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0146] Disperse bleached wood pulp in water (solid content 10wt%), add TEMPO (wood pulp: TEMPO = 50:1 w / w) and sodium bromide (wood pulp: NaBr = 5:1 w / w);

[0147] Drop in 8wt% sodium hypochlorite solution to pH = 10.0±0.2, react for 5h;

[0148] Terminate the reaction with 0.5M hydrochloric acid, centrifugal washing to obtain carboxylated nanocellulose;

[0149] Carboxylated nanocellulose reacts with sodium sulfite (CNF-COOH:Na2SO3 = 1:0.08 w / w) at 79-81℃ for 2h;

[0150] Freeze-drying (-55℃, 8Pa), spray 0.2% triethyl citrate ethanol solution, cross-linking and reinforcement, 75℃ heat treatment for 25min.

[0151] In specific implementation, the preparation steps of the metal organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0152] Dissolve 2-methylimidazole in methanol (concentration 2wt%), add silver nitrate (2-methylimidazole: AgNO3 = 4:1 w / w), stir for 25-35min;

[0153] Drop in methanol solution containing zinc nitrate hexahydrate (2-methylimidazole: zinc nitrate hexahydrate = 2:1 w / w), react at 22℃ for 18h;

[0154] Centrifugal (7000rpm, 10min), wash with methanol three times, dry at 60℃;

[0155] Put into stearic acid / ethanol solution (concentration 2wt%) for impregnation (solid to liquid ratio 1:10), oscillate at 55℃ for 2h, vacuum drying, stearic acid coating forms monolayer protection skeleton.

[0156] Further, the nanocellulose aerogel and the metal organic framework silver-loaded particles are compounded by freezing electron beam irradiation:

[0157] The nanocellulose aerogel is immersed in an EVA / toluene solution containing 4wt% metal organic framework silver-loaded particles;

[0158] Frozen in liquid nitrogen to-196℃, 9kGy electron beam irradiation;

[0159] After thawing at room temperature, drying forms an interpenetrating network structure.

[0160] Example 3

[0161] The embodiment of the present application provides a multilayer anti-fog heat-shrinkable polyolefin sealing film, comprising a multilayer co-extrusion structure:

[0162] The contact layer comprises a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid, and a dynamic borate anti-fog agent.

[0163] The functional layer comprises modified diatomite and nano calcium carbonate.

[0164] The protective layer comprises nanocellulose aerogel and metal organic framework silver-loaded particles.

[0165] In the embodiment, the contact layer comprises, by weight parts, 70 parts of metallocene linear low density polyethylene, 6 parts of modified cyclodextrin-poly ionic liquid, 3 parts of dynamic borate anti-fog agent, 1.5 parts of nano silicon dioxide, 0.5 parts of acetylacetone aluminum, and 0.2 parts of sodium pyrophosphate.

[0166] The functional layer comprises, by weight parts, 30 parts of polypropylene, 50 parts of low density polyethylene, 15 parts of modified diatomite, 10 parts of nano calcium carbonate, and 0.75 parts of erucamide.

[0167] The protective layer comprises, by weight parts, 65 parts of low density polyethylene, 20 parts of ethylene-vinyl acetate copolymer, 8 parts of nanocellulose aerogel, and 2 parts of metal organic framework silver-loaded particles.

[0168] The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment, as shown in the formula (I), comprises the following steps: Figure 1

[0169] (1) Raw material preparation and mixing: prepare raw materials of each layer according to the formula;

[0170] (2) Melt co-extrusion: multilayer co-extrusion, and the temperature control of each layer is as follows:

[0171] The temperature zone of the contact layer extruder: feeding zone 150℃→melting zone 165℃→homogenization zone 170℃.

[0172] ​Functional layer extruder temperature zone: feeding zone 155℃→ melting zone 195℃→ homogenization zone 185℃;

[0173] Protective layer extruder temperature zone: feeding zone 145℃→ melting zone 160℃→ homogenization zone 175℃;

[0174] Die connecting body temperature: 170℃;

[0175] (3) Supercritical CO2 quenching: injecting supercritical CO2 (temperature 31℃, pressure 7.4MPa) in the sharp cooling section;

[0176] (4) Asynchronous bidirectional gradient stretching: longitudinal 1.5 times pre-stretching (90℃), infrared gradient heating to 112.5℃, transverse 3.2 times secondary stretching;

[0177] (5) Alternating electric field aging treatment: frequency 20-100Hz, field strength 4-6kV / cm, time 30min;

[0178] (6) Winding and slitting.

[0179] The preparation steps of the modified cyclodextrin-polyionic liquid are as follows:

[0180] Dissolve β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:5), add 4-vinylbenzyl chloride (molar ratio of β-cyclodextrin to 4-vinylbenzyl chloride is 1:0.3), and react at 70℃ for 12h;

[0181] Pour the reaction solution into ice ethanol to precipitate, and filter to obtain vinyl cyclodextrin;

[0182] Mix vinyl cyclodextrin with 1-vinyl-3-ethyl imidazole bromide salt according to a molar ratio of 1:5, add 0.15mol% azobisisobutyronitrile, and polymerize at 60℃ under nitrogen protection for 19h;

[0183] Wash with ethanol three times, and dry at 60℃ under vacuum.

[0184] Further, the preparation steps of the dynamic borate antifogging agent are as follows:

[0185] Dissolve 4-vinylphenylboronic acid in tetrahydrofuran (mass ratio 1:4), add sorbitol (molar ratio of 4-vinylphenylboronic acid to sorbitol is 1:0.4) and 0.5wt% p-toluenesulfonic acid;

[0186] Reflux at 80℃ for 7h, and remove tetrahydrofuran by rotary evaporation;

[0187] Wash with acetone three times to obtain a transparent viscous liquid.

[0188] Still further, the preparation steps of the modified diatomite are as follows:

[0189] Mixing diatomite with 12.5wt% hydrochloric acid at a mass ratio of 1:6.5, stirring and reacting in a microwave reactor at 80℃ for 45min (power 750W), centrifugal separation, and washing with deionized water until neutral to obtain expanded diatomite;

[0190] Grading by weight, taking 100 parts of expanded diatomite, adding 5 times the weight of anhydrous ethanol, ultrasonic treatment (45kHz, 35min), adding a titanate coupling agent, and refluxing at 74℃ for 1.75h;

[0191] Adding an ethanol solution of stearic acid (concentration 5wt%) dropwise, continuing to react for 1h, suction filtration, and vacuum drying at 65℃ for 12h;

[0192] Grinding in a ball mill with zirconia balls (Φ3mm, ball-to-material ratio 5:1, rotation speed 250rpm, time 45min) to obtain modified diatomite.

[0193] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0194] Dispersing bleached wood pulp in water (solid content 12.5wt%), adding TEMPO (wood pulp:TEMPO=52.5:1w / w) and sodium bromide (wood pulp:NaBr=5:1w / w);

[0195] Adding an 8-12wt% sodium hypochlorite solution dropwise to pH=10.0, and reacting for 5.5h;

[0196] Terminating the reaction with 0.5M hydrochloric acid, and centrifugal washing to obtain carboxylated nanocellulose;

[0197] Carboxylated nanocellulose and sodium sulfite (CNF-COOH:Na2SO3=1:0.1w / w) are reacted at 80℃ for 2.5h;

[0198] Freeze-drying (-50℃, 10Pa), spraying 0.3% triethyl citrate ethanol solution, crosslinking and reinforcement, and heat treatment at 80℃ for 30min.

[0199] In a specific implementation, the preparation steps of the metal-organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0200] Dissolving 2-methylimidazole in methanol (concentration 2.5wt%), adding silver nitrate (2-methylimidazole:AgNO3=5:1w / w), and stirring for 30min;

[0201] Adding a methanol solution containing zinc nitrate hexahydrate (2-methylimidazole:zinc nitrate hexahydrate=2.5:1w / w) dropwise, and reacting at 24℃ for 21h;

[0202] Centrifugal separation (8000rpm, 12.5min), washing with methanol three times, and drying at 60℃;

[0203] Put into stearic acid / ethanol solution (concentration 2wt%) impregnation (solid-liquid ratio 1:10), 60℃ oscillation 2h, vacuum drying, stearic acid coating forms a monolayer protection skeleton.

[0204] Further, the nanocellulose aerogel and the metal organic framework silver-loaded particles are compounded by freezing electron beam irradiation:

[0205] The nanocellulose aerogel is immersed in an EVA / toluene solution containing 5wt% metal organic framework silver-loaded particles;

[0206] Liquid nitrogen is frozen to-196℃, and 10kGy electron beam irradiation is performed;

[0207] After thawing at room temperature, drying is performed to form an interpenetrating network structure.

[0208] Example 4

[0209] The embodiment of the present application provides a multilayer anti-fog heat-shrinkable polyolefin sealing film, which comprises a multilayer co-extrusion structure:

[0210] The contact layer comprises a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid, and a dynamic borate anti-fog agent.

[0211] The functional layer comprises modified diatomite and nano calcium carbonate.

[0212] The protective layer comprises nanocellulose aerogel and metal organic framework silver-loaded particles.

[0213] In the embodiment, the contact layer comprises, by weight parts, 72 parts of metallocene linear low-density polyethylene, 6.5 parts of modified cyclodextrin-poly ionic liquid, 3.5 parts of dynamic borate anti-fog agent, 1.8 parts of nano silicon dioxide, 0.6 parts of acetylacetone aluminum, and 0.25 parts of sodium pyrophosphate.

[0214] The functional layer comprises, by weight parts, 33 parts of polypropylene, 52 parts of low-density polyethylene, 18 parts of modified diatomite, 11 parts of nano calcium carbonate, and 0.9 parts of erucamide.

[0215] The protective layer comprises, by weight parts, 68 parts of low-density polyethylene, 23 parts of ethylene-vinyl acetate copolymer, 8.5 parts of nanocellulose aerogel, and 2.5 parts of metal organic framework silver-loaded particles.

[0216] The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment is as shown in the following formula: Figure 1 The preparation method comprises the following steps:

[0217] (1) Raw material preparation and mixing: prepare raw materials of each layer according to the formula;

[0218] (2) melt co-extrusion: multi-layer co-extrusion, the temperature control of each layer is as follows:

[0219] The temperature zone of the contact layer extruder is: feeding zone 152℃→ melting zone 167℃→ homogenization zone 172℃;

[0220] The temperature zone of the functional layer extruder is: feeding zone 157℃→ melting zone 197℃→ homogenization zone 187℃;

[0221] The temperature zone of the protective layer extruder is: feeding zone 147℃→ melting zone 162℃→ homogenization zone 177℃;

[0222] The temperature of the die connecting body is: 172℃;

[0223] (3) supercritical CO2 quenching: injecting supercritical CO2 (temperature 32℃, pressure 7.6MPa) in the sharp cooling section;

[0224] (4) asynchronous bidirectional gradient stretching: longitudinal 1.6 times pre-stretching (95℃), infrared gradient heating to 115℃, and transverse 3.4 times secondary stretching;

[0225] (5) alternating electric field aging treatment: frequency 20-100Hz, field strength 4-6kV / cm, time 40min;

[0226] (6) winding and slitting.

[0227] The preparation steps of the modified cyclodextrin-polyionic liquid are as follows:

[0228] Dissolve β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:6), add 4-vinylbenzyl chloride (the molar ratio of β-cyclodextrin to 4-vinylbenzyl chloride is 1:0.4), and react at 72℃ for 12.5h;

[0229] Pour the reaction solution into ice ethanol for precipitation, and filter to obtain vinyl cyclodextrin;

[0230] Mix vinyl cyclodextrin and 1-vinyl-3-ethyl imidazole bromide salt according to a molar ratio of 1:6, add 0.2mol% azobisisobutyronitrile, and polymerize at 61℃ under nitrogen protection for 20h;

[0231] Wash with ethanol for three times, and dry at 60℃ under vacuum.

[0232] Further, the preparation steps of the dynamic borate antifogging agent are as follows:

[0233] Dissolve 4-vinylphenylboronic acid in tetrahydrofuran (mass ratio 1:5), add sorbitol (the molar ratio of 4-vinylphenylboronic acid to sorbitol is 1:0.5) and 0.5wt% p-toluenesulfonic acid;

[0234] Reflux at 82℃ for 8h, and remove tetrahydrofuran by rotary evaporation;

[0235] Washing with acetone three times, a transparent viscous liquid was obtained.

[0236] Further, the preparation steps of the modified diatomite are as follows:

[0237] The diatomite was mixed with 15wt% hydrochloric acid at a mass ratio of 1:8, stirred and reacted in a microwave reactor at 85°C for 50min (power 800W), centrifuged, and washed with deionized water until neutral to obtain expanded diatomite;

[0238] According to weight classification, 110 parts of the expanded diatomite were added into 6 times weight of anhydrous ethanol, ultrasonically treated (40-50kHz, 30-40min), and a titanate coupling agent was added, and refluxed at 78°C for 2h;

[0239] Ethanol solution of stearic acid (concentration 6wt%) was added dropwise, and the reaction was continued for 1h, and then filtered, and vacuum dried at 70°C for 12h;

[0240] Zirconia balls (Φ3mm, ball-to-material ratio 5:1, rotation speed 250rpm, time 50min) were used for ball milling to obtain the modified diatomite.

[0241] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0242] Bleached wood pulp was dispersed in water (solid content 15wt%), and TEMPO (wood pulp:TEMPO=55:1w / w) and sodium bromide (wood pulp:NaBr=5:1w / w) were added;

[0243] 12wt% sodium hypochlorite solution was added dropwise to pH=10.2, and the reaction was continued for 6h;

[0244] The reaction was terminated with 0.5M hydrochloric acid, and centrifuged and washed to obtain carboxylated nanocellulose;

[0245] The carboxylated nanocellulose was reacted with sodium sulfite (CNF-COOH:Na2SO3=1:0.12w / w) at 79-81°C for 3h;

[0246] Freeze-drying (-45°C, 12Pa), spraying 0.4% triethyl citrate ethanol solution, cross-linking and reinforcement, and heat treatment at 85°C for 35min.

[0247] In specific implementation, the preparation steps of the metal organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0248] 2-methylimidazole was dissolved in methanol (concentration 3wt%), and silver nitrate was added (2-methylimidazole:AgNO3=6:1w / w), and stirred for 35min;

[0249] Drop methanol solution containing zinc nitrate hexahydrate (2-methyl imidazole: zinc nitrate hexahydrate = 3:1 w / w), 26℃ reaction for 24h;

[0250] Centrifugation (9000rpm, 15min), methanol washing three times, drying at 60℃;

[0251] Put into stearic acid / ethanol solution (concentration 2wt%), immerse (solid-liquid ratio 1:10), oscillate at 65℃ for 2h, vacuum drying, stearic acid coating forms monolayer protection skeleton.

[0252] Further, the nanocellulose aerogel and metal organic framework silver-loaded particles are compounded by freezing electron beam irradiation:

[0253] Immerse the nanocellulose aerogel in EVA / toluene solution containing 6wt% metal organic framework silver-loaded particles;

[0254] Freeze in liquid nitrogen to-196℃, 11kGy electron beam irradiation;

[0255] Drying after thawing at room temperature, forming an interpenetrating network structure.

[0256] Example 5

[0257] The embodiment of the present application provides a multilayer anti-fog heat-shrinkable polyolefin sealing film, comprising a multilayer co-extrusion structure:

[0258] The contact layer comprises a metallocene polyolefin, a modified cyclodextrin-poly ionic liquid, and a dynamic borate anti-fog agent.

[0259] The functional layer comprises modified diatomite and nano calcium carbonate.

[0260] The protective layer comprises nanocellulose aerogel and metal organic framework silver-loaded particles.

[0261] In the embodiment, the contact layer comprises, by weight parts, 75 parts of metallocene linear low-density polyethylene, 7 parts of modified cyclodextrin-poly ionic liquid, 4 parts of dynamic borate anti-fog agent, 2 parts of nano silicon dioxide, 0.7 parts of acetylacetone aluminum, and 0.3 parts of sodium pyrophosphate.

[0262] The functional layer comprises, by weight parts, 35 parts of polypropylene, 55 parts of low-density polyethylene, 20 parts of modified diatomite, 12 parts of nano calcium carbonate, and 0.1 parts of erucamide.

[0263] The protective layer comprises, by weight parts, 70 parts of low-density polyethylene, 25 parts of ethylene-vinyl acetate copolymer, 9 parts of nanocellulose aerogel, and 3 parts of metal organic framework silver-loaded particles.

[0264] The preparation method of the multilayer anti-fog heat-shrinkable polyolefin sealing film in the embodiment is as follows: Figure 1The preparation method comprises the following steps as shown in the figure:

[0265] (1) Raw material preparation and mixing: prepare raw materials for each layer according to the formula;

[0266] (2) Melt co-extrusion: multi-layer co-extrusion, and the temperature control of each layer is as follows:

[0267] The temperature zone of the contact layer extruder: feeding zone 152℃→ melting zone 167℃→ homogenization zone 172℃;

[0268] The temperature zone of the functional layer extruder: feeding zone 157℃→ melting zone 197℃→ homogenization zone 187℃;

[0269] The temperature zone of the protective layer extruder: feeding zone 147℃→ melting zone 162℃→ homogenization zone 177℃;

[0270] The temperature of the die connecting body: 172℃;

[0271] (3) Supercritical CO2 quenching: inject supercritical CO2 (temperature 32℃, pressure 7.6MPa) in the sharp cooling section;

[0272] (4) Asynchronous bidirectional gradient stretching: longitudinal 1.6 times pre-stretching (95℃), infrared gradient heating to 115℃, and transverse 3.4 times secondary stretching;

[0273] (5) Alternating electric field aging treatment: frequency 20-100Hz, field strength 4-6kV / cm, and time 40min;

[0274] (6) Winding and slitting.

[0275] The preparation steps of the modified cyclodextrin-polyionic liquid are as follows:

[0276] Dissolve β-cyclodextrin in dimethyl sulfoxide (mass ratio 1:6), add 4-vinylbenzyl chloride (the molar ratio of β-cyclodextrin to 4-vinylbenzyl chloride is 1:0.4), and react at 72℃ for 12.5h;

[0277] Pour the reaction solution into ice ethanol for precipitation, and filter to obtain vinyl cyclodextrin;

[0278] Mix vinyl cyclodextrin and 1-vinyl-3-ethyl imidazole bromide salt according to a molar ratio of 1:6, add 0.2mol% azobisisobutyronitrile, and polymerize at 61℃ under nitrogen protection for 20h;

[0279] Wash with ethanol for three times, and dry at 60℃ under vacuum.

[0280] Further, the preparation steps of the dynamic borate antifogging agent are as follows:

[0281] 4-vinylphenylboronic acid was dissolved in tetrahydrofuran (mass ratio 1:5), sorbitol was added (molar ratio of 4-vinylphenylboronic acid to sorbitol was 1:0.5), and 0.5wt% p-toluenesulfonic acid was added;

[0282] 82℃ backflow reaction for 8h, rotary evaporation to remove tetrahydrofuran;

[0283] Washed with acetone three times, and a transparent viscous liquid was obtained.

[0284] Further, the preparation steps of the modified diatomite are as follows:

[0285] The diatomite was mixed with 15wt% hydrochloric acid at a mass ratio of 1:8, stirred at 85℃ in a microwave reactor for 50min (power 800W), centrifuged, and washed with deionized water until neutral to obtain expanded diatomite;

[0286] Graded by weight, 110 parts of expanded diatomite were added to 6 times the weight of anhydrous ethanol, ultrasonically treated (40-50kHz, 30-40min), and a titanate coupling agent was added, refluxed at 78℃ for 2h;

[0287] Ethanol solution of stearic acid (concentration 6wt%) was added dropwise, and the reaction was continued for 1h, then filtered, and vacuum dried at 70℃ for 12h;

[0288] Zirconia balls (Φ3mm, ball-to-material ratio 5:1, rotation speed 250rpm, time 50min) were used for ball milling to obtain modified diatomite.

[0289] Preferably, the preparation steps of the nanocellulose aerogel are as follows:

[0290] Bleached wood pulp was dispersed in water (solid content 15wt%), TEMPO (wood pulp: TEMPO = 55:1 w / w) and sodium bromide (wood pulp: NaBr = 5:1 w / w) were added;

[0291] 12wt% sodium hypochlorite solution was added dropwise to pH = 10.2, and the reaction was continued for 6h;

[0292] The reaction was terminated with 0.5M hydrochloric acid, and the carboxylated nanocellulose was washed by centrifugation;

[0293] Carboxylated nanocellulose was reacted with sodium sulfite (CNF-COOH:Na2SO3 = 1:0.12 w / w) at 79-81℃ for 3h;

[0294] Freeze-dried (-45℃, 12Pa), sprayed with 0.4% triethyl citrate ethanol solution, crosslinked and reinforced, and heat treated at 85℃ for 35min.

[0295] In specific implementation, the preparation steps of the metal-organic framework silver-loaded particles (Ag@ZIF-8) are as follows:

[0296] 2-methylimidazole was dissolved in methanol (concentration 3wt%), silver nitrate was added (2-methylimidazole: AgNO3=6:1w / w), stirring for 35min;

[0297] methanol solution containing zinc nitrate hexahydrate (2-methylimidazole: zinc nitrate hexahydrate = 3:1w / w) was added dropwise, and the reaction was carried out at 26℃ for 24h;

[0298] centrifugation (9000rpm, 15min), methanol washing three times, drying at 60℃;

[0299] immersed in stearic acid / ethanol solution (concentration 2wt%) (solid-liquid ratio 1:10), oscillation at 65℃ for 2h, vacuum drying, stearic acid coating formed monolayer protection skeleton.

[0300] Further, the nanocellulose aerogel and metal organic framework silver-loaded particles were compounded by freeze electron beam irradiation:

[0301] The nanocellulose aerogel was immersed in an EVA / toluene solution containing 6wt% metal organic framework silver-loaded particles;

[0302] Frozen in liquid nitrogen to-196℃, 11kGy electron beam irradiation;

[0303] Drying after thawing at room temperature, forming an interpenetrating network structure.

[0304] Comparative Example 1: The contact layer cancels the dynamic borate antifog agent and uses sorbitan monooleate instead, and the others are the same as Example 3.

[0305] Comparative Example 2: The contact layer cancels the modified cyclodextrin-polyionic liquid, and the antifog agent is directly blended, and the others are the same as Example 3.

[0306] Comparative Example 3: The functional layer replaces the modified diatomite with ordinary diatomite, and the others are the same as Example 3.

[0307] Comparative Example 4: The functional layer cancels the nanometer calcium carbonate, and the antifog agent is directly blended, and the others are the same as Example 3.

[0308] Comparative Example 5: The protective layer cancels the nanocellulose aerogel, and the others are the same as Example 3.

[0309] Comparative Example 6: The protective layer cancels the metal organic framework silver-loaded particles, and the others are the same as Example 3.

[0310] Comparative Example 7: Cancel supercritical CO2 quenching and use 5℃ water cooling instead, and the others are the same as Example 3.

[0311] Comparative Example 8: Cancel the alternating electric field aging, and the others are the same as Example 3.

[0312] Performance test

[0313] Test items and standards

[0314] Anti-fog durability GB / T 31726

[0315] Gloss (60°) ASTM D2457

[0316] Haze ASTM D1003

[0317] Heat shrinkage ASTM D2732 90℃ water bath / 10s.

[0318] The test results are shown in Table 1 below:

[0319] Table 1

[0320]

[0321] From the above results, it can be seen that the sealing film prepared by the present application has good anti-fog performance, low haze and high light transmittance.

[0322] It should be noted that, for the foregoing embodiments, in order to simply describe, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the order of the described actions, because according to the present application, certain steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification all belong to preferred embodiments, and the actions and modules involved are not necessarily necessary for the present application.

[0323] The above examples are only used to illustrate the technical solutions of the present application, and do not limit the protection scope of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art can still combine, add or delete the features of the embodiments of the present application according to the circumstances without creative labor, so as to obtain different other technical solutions which do not deviate from the concept of the present application in essence. These technical solutions also belong to the scope of the present application.

Claims

1. A multilayer anti-fog heat-shrinkable polyolefin sealing film, characterized in that, Including multi-layer co-extruded structures: The contact layer, by weight, comprises: 65-75 parts of metallocene linear low-density polyethylene, 5-7 parts of modified cyclodextrin-polyionic liquid, 2-4 parts of dynamic borate antifogging agent, and 1-2 parts of nano silica. The functional layer, by weight, comprises: 25-35 parts polypropylene, 45-55 parts low-density polyethylene, 10-20 parts modified diatomaceous earth, 8-12 parts nano-calcium carbonate, and 0.5-1 parts erucamide. Protective layer: by weight, it includes: 60-70 parts low-density polyethylene, 15-25 parts ethylene-vinyl acetate copolymer, 7-9 parts nanocellulose aerogel, and 1-3 parts metal-organic framework silver particles.

2. The multilayer anti-fog heat-shrinkable polyolefin sealing film as described in claim 1, characterized in that, The preparation steps of the modified cyclodextrin-polyionic liquid are as follows: β-cyclodextrin was dissolved in dimethyl sulfoxide, and 4-vinylbenzyl chloride was added to initiate the reaction. The reaction solution was poured into ice-cold ethanol to precipitate the product, and then filtered to obtain vinyl cyclodextrin. Vinyl cyclodextrin was mixed with 1-vinyl-3-ethylimidazolium bromide, and azobisisobutyronitrile was added. Polymerization was carried out under nitrogen protection. Wash three times with ethanol and then vacuum dry.

3. The multilayer anti-fog heat-shrinkable polyolefin sealing film as described in claim 1, characterized in that, The preparation steps of the dynamic borate ester antifogging agent are as follows: Dissolve 4-vinylphenylboronic acid in tetrahydrofuran, then add sorbitol and p-toluenesulfonic acid; Reflux reaction and rotary evaporation to remove tetrahydrofuran; Wash three times with acetone to obtain a clear, viscous liquid.

4. The multilayer anti-fog heat-shrinkable polyolefin sealing film as described in claim 1, characterized in that, The preparation steps of the modified diatomaceous earth are as follows: Diatomaceous earth is mixed with hydrochloric acid, stirred and reacted in a microwave reactor, separated by centrifugation, and washed with deionized water until neutral to obtain expanded pore diatomaceous earth. According to weight classification, take the expanded diatomaceous earth, add it to anhydrous ethanol, sonicate it, add titanate coupling agent, and reflux. Add stearic acid ethanol solution dropwise, continue the reaction, filter, and dry under vacuum; Modified diatomaceous earth was obtained by grinding with zirconia balls in a ball mill.

5. The multilayer anti-fog heat-shrinkable polyolefin sealing film as described in claim 1, characterized in that, The preparation steps of the nanocellulose aerogel are as follows: Disperse bleached wood pulp in water, and add TEMPO and sodium bromide; Add sodium hypochlorite solution dropwise until pH = 10.0 ± 0.2, and allow the reaction to proceed. The reaction was terminated with hydrochloric acid, and the carboxylated nanocellulose was obtained by centrifugation and washing. Carboxylated cellulose nanoparticles react with sodium sulfite; Freeze-drying, spray application of triethyl citrate ethanol solution, cross-linking reinforcement, and heat treatment.

6. The multilayer anti-fog heat-shrinkable polyolefin sealing film as described in claim 5, characterized in that, The preparation steps of the silver-loaded metal-organic framework particles are as follows: Dissolve 2-methylimidazole in methanol, add silver nitrate, and stir; Add a methanol solution containing zinc nitrate hexahydrate dropwise, and the reaction proceeds. Centrifuge, wash three times with methanol, and dry; Immerse in an ethanol solution of stearic acid, shake, and vacuum dry; The nanocellulose aerogel was composited with silver-loaded metal-organic framework particles via cryo-electron beam irradiation.

7. The method for preparing the multilayer anti-fogging heat-shrinkable polyolefin sealing film according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Raw material preparation and mixing: Prepare the raw materials for each layer according to the formula; (2) Melt co-extrusion: multi-layer co-extrusion; (3) Supercritical CO2 quenching: Supercritical CO2 is injected into the rapid cooling section; (4) Asynchronous bidirectional gradient stretching: longitudinal pre-stretching 1.4-1.6 times, infrared gradient heating to 110-115℃, transverse secondary stretching 3.0-3.4 times; (5) Aging treatment of alternating electric field: frequency 20-100Hz, field strength 4-6kV / cm, time 20-40min; (6) Rolling up and cutting.

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