Preparation method of food heat-preservation environment-friendly fast-transportation packaging bag

Abstract

The invention relates to the technical field of packaging materials, in particular to a preparation method of a food heat-preservation environment-friendly quick-transportation packaging bag. The prepared quick-transportation packaging bag sequentially comprises an outer film layer, a heat preservation layer, an aluminum foil layer and an inner film layer from outside to inside. The outer film layer and the inner film layer are made of a blend of polylactic acid, carboxymethyl starch and glycerol, the thermal insulation layer is formed by compounding a phase change capsule, silicon dioxide aerogel and a polyurethane adhesive on an aluminum foil layer, the phase change capsule takes a mixture of n-octadecane and paraffin as a core material and takes Arabic gum as a wall material, and the outer surface of the wall material is coated with a stearic acid film layer; an antibacterial coating containing microwave modified beewax, a functional additive and 3-aminopropyltriethoxysilane is sprayed on the inner surface of the inner film layer; the prepared quick-transportation packaging bag has excellent heat preservation performance and antibacterial performance, also has good degradability, is environmentally friendly and can meet multiple requirements of modern food logistics for packaging.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, in particular to a method for preparing a heat-insulating and environment-friendly express packaging bag for food. Background Art

[0002] With the booming food delivery industry and fresh food e-commerce, the need for keeping food warm and fresh during transportation is becoming increasingly prominent. Traditional food packaging bags, which mostly only provide basic packaging functions, are unable to effectively maintain food temperature during transportation, resulting in reduced food quality and taste. They can even cause microbial growth due to inappropriate temperatures, compromising food safety.

[0003] At the same time, traditional packaging bags have shortcomings in terms of environmental performance, and the extensive use of non-degradable materials has placed a heavy burden on the environment. Polylactic acid, a fully biodegradable aliphatic polyester polymer with excellent biocompatibility, has gradually become a research hotspot for environmentally friendly packaging materials. However, pure polylactic acid has shortcomings in thermal insulation and antibacterial properties, limiting its application in food insulation and express delivery packaging.

[0004] Based on this, the present invention provides a method for preparing a food insulation and environmentally friendly express transportation packaging bag, aiming to solve the above-mentioned technical problems. Summary of the Invention

[0005] The express packaging bag prepared by the present invention not only has excellent heat preservation and antibacterial properties, but also has good degradability, is relatively environmentally friendly, and can meet the multiple packaging requirements of modern food logistics.

[0006] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a food heat-insulating and environment-friendly express packaging bag comprises the following steps: Step 1: polylactic acid, carboxymethyl starch and glycerol are mixed in a mass ratio of 70-85:15-30:3-8, and melt-extrusion blow molding is performed to form an outer film layer with a thickness of 50-100 μm and an inner film layer with a thickness of 30-80 μm; Step 2: Mixing phase change capsules with polyurethane adhesive in a mass ratio of 0.3-0.6:1, adding 0.05-1% of a defoamer and 10-15% of a silica aerogel to the resulting mixture, mixing well, and coating the mixture on the surface of the aluminum foil layer. After drying, the insulation layer is obtained; wherein the phase change capsules use a mixture of n-octadecane and paraffin as a core material, gum arabic as a wall material, and the outer surface of the wall material is coated with a stearic acid film layer; Step 3: Hot-press the insulation layer and the outer film layer, adhere the inner film layer to the aluminum foil layer with a polyurethane adhesive, then electrostatically spray antibacterial liquid on the inner layer of the inner film layer, cut the resulting composite material after drying, and finally use high-frequency welding to make packaging bags.

[0007] Furthermore, the antibacterial liquid is prepared by mixing microwave-modified beeswax with a dispersion liquid with a volume 4-6 times that of the beeswax and a temperature of 70-75°C; wherein the dispersion liquid is prepared by mixing an ethanol aqueous solution with a volume concentration of 60-80% and Tween 80 with a mass ratio of 2-4%, a functional additive of 50-60%, and 3-aminopropyltriethoxysilane with a mass ratio of 5-8%.

[0008] Furthermore, the preparation method of the functional additive is: Step 1: Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (1.5-2 times the mass of chitosan) to the chitosan solution, mix well, adjust the pH to 8.5-9.5, and react at 60-80° C. for 8-12 hours; then dialyze and freeze-dry the resulting components to obtain a modifier; Step 2: The amino titanium dioxide aerogel is uniformly dispersed in a phosphate buffer solution with a pH of 7.4 at a concentration of 3-6wt%, and a glutaraldehyde aqueous solution with a mass of 2-3% and a concentration of 25wt% of the amino titanium dioxide aerogel is added. After stirring at 30-40°C for 3-5h, a modifier with a mass of 0.2-0.4 times that of the amino titanium dioxide aerogel is added. After reacting at 50-60°C for 8-12h, the reaction product is centrifuged and freeze-dried to obtain a functional additive.

[0009] Furthermore, the preparation method of the amino titanium dioxide aerogel is as follows: the titanium dioxide aerogel is uniformly dispersed in an ethanol aqueous solution with a volume concentration of 80-90% at a dosage ratio of 30-80 g / L, and then a silane coupling agent KH-550 is added with a mass of 30-40% of the titanium dioxide aerogel. After reflux reaction for 4-6 hours, the reaction product is centrifuged, washed and dried in sequence.

[0010] Furthermore, the preparation method of titanium dioxide aerogel is as follows: 10-20g / L of lauryltrimethylammonium bromide aqueous solution is mixed with ammonia water and mesitylene in a volume ratio of 500-800:1:5-10, and the mixture is stirred at 500-1000r / min at a temperature of 25-35°C for 3-5h; then, tetrabutyl titanate with an equal volume of mesitylene is added dropwise to the obtained mixture, and the mixture is stirred at 30-40°C for 20-30h; after the reaction is completed, the obtained reaction product is gelled at 50-60°C for 10-15h, and then calcined and ball-milled to obtain titanium dioxide aerogel.

[0011] Furthermore, the chitosan solution is prepared by adding acetic acid to the chitosan aqueous solution and stirring at 40-60° C. for 1-2 hours to obtain the chitosan solution; wherein the feed ratio of chitosan, water, and acetic acid is 2-5 g:100 mL:1-2.5 mL.

[0012] Furthermore, the thickness of the aluminum foil layer and the insulation layer in step 2 are 10-50 μm and 0.8-1.2 mm respectively; the coating amount is 100-180 g / m 2 , the drying temperature is 60-90℃.

[0013] Furthermore, the preparation method of the phase change capsule is as follows: n-octadecane and paraffin are mixed in a mass ratio of 2-4:1 and heated until completely melted, and then cooled to room temperature as a core material; gum arabic is dissolved in deionized water with a mass of 20-50 times that of the gum arabic and a temperature of 50-60°C to prepare a wall material solution; the core material and the wall material solution are mixed and the pH is adjusted to 4-4.5, and the reaction is stirred at 50-60°C for 3-5 hours; after the reaction is completed, the reaction product is cooled, centrifuged, washed and dried in sequence; finally, a layer of stearic acid is melt-coated on the surface of the obtained solid material with a particle size of 8-12 μm, and the phase change capsule is obtained after cooling and solidification.

[0014] Furthermore, the preparation method of the microwave-modified beeswax is as follows: at a microwave power of 500-1000W, the beeswax is irradiated 2-4 times in an intermittent irradiation manner, with each treatment time being 20-40s.

[0015] Furthermore, in step 3, the hot pressing temperature during hot pressing and laminating is 110-150° C., the pressure is 0.5-3 MPa, and the hot pressing time is 10-30 s.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses lauryltrimethylammonium bromide aqueous solution, ammonia water, mesitylene, and tetrabutyl titanate as raw materials to prepare titanium dioxide aerogel with mesoporous properties. The titanium dioxide aerogel is then modified using a silane coupling agent KH-550 to introduce active groups on its surface, thereby preparing an amino titanium dioxide aerogel. The amino titanium dioxide aerogel is placed in a buffer solution and a modifier prepared by reacting chitosan and 3-chloro-2-hydroxypropyltrimethylammonium chloride is added. Finally, under the "bridge" effect of glutaraldehyde, the modifier is grafted onto the surface of the amino titanium dioxide aerogel and the inner wall of its porous structure, forming a relatively dense three-dimensional antibacterial network structure on the surface and inside of the titanium dioxide aerogel, effectively improving the antibacterial properties of the titanium dioxide aerogel while also reducing the probability of it falling off. The prepared functional additive has excellent antibacterial properties under the synergistic effect of the titanium dioxide aerogel and the modifier. More importantly, the prepared functional additive uses titanium dioxide aerogel as raw material, which works synergistically with silicon dioxide aerogel and aluminum foil layer, so that the prepared packaging bag has excellent thermal insulation performance.

[0017] 2. Microwave irradiation partially breaks the ester bonds in beeswax, generating more short-chain fatty acids (such as palmitic acid and propolis acid) and free alcohols. These components not only have a stronger destructive effect on bacterial cell membranes but also enhance its solubility in aqueous ethanol. Furthermore, microwave irradiation activates the beeswax surface, increasing its polar groups, such as hydroxyl groups, and strengthening its electrostatic adsorption to bacterial cell walls. This enhances its compatibility with polylactic acid and titanium dioxide aerogel, improving the adhesion of the antibacterial coating. The synergistic effect between microwave-modified beeswax and the functional additives effectively ensures the antibacterial properties of the prepared express delivery packaging bags.

[0018] 3. The phase-change capsules prepared in this invention use a mixture of n-octadecane and paraffin as the core material and gum arabic as the wall material. The outer surface of the wall material is coated with a stearic acid film. The presence of the stearic acid film allows the phase-change capsules to be more evenly dispersed in the polyurethane adhesive system, reducing the chance of agglomeration. The phase-change capsules achieve temperature control through a reversible solid-liquid phase transition process. When the temperature of the packaged food exceeds the phase transition point, the composite core material (the n-octadecane and paraffin mixture) within the capsule absorbs heat and undergoes a solid-liquid phase transition, converting the sensible heat released by the food into latent heat for storage. When the ambient temperature drops, the core material releases this stored latent heat, undergoing a liquid-solid phase transition, thus forming a dynamic temperature buffering mechanism. This phase transition process maintains a near-isothermal state within a specific temperature range (25-45°C), allowing food at 60°C to remain above 55°C for up to three hours in a 25°C environment, more than doubling the effective insulation time compared to traditional insulation materials. Furthermore, the dual protection of a gum arabic wall material and a stearic acid coating ensures both the stability of the phase change material packaging in its liquid state (leakage rate <5% after 100 hot and cold cycles) and its efficient thermal conductivity. When used in conjunction with the aerogel insulation layer in the packaging, the phase change capsule primarily slows temperature changes through convective heat buffering, while the aerogel layer inhibits heat conduction through its nanoporous structure. The two synergistically form a composite insulation mechanism of "molecular-level energy storage + microstructural heat resistance." This design not only provides excellent thermal insulation but also offers more precise temperature control capabilities (temperature fluctuation range ±2°C), perfectly meeting the lightweight and environmentally friendly demands of modern food logistics.

[0019] In summary, the express packaging bag prepared by the present invention not only has excellent thermal insulation and antibacterial properties, but also has good biodegradability, is relatively environmentally friendly, and can meet the multiple packaging requirements of modern food logistics. DETAILED DESCRIPTION

[0020] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Example 1 To achieve the above object, the present invention provides the following technical solutions: A method for preparing a food heat-insulating and environment-friendly express packaging bag comprises the following steps: Step 1: polylactic acid, carboxymethyl starch and glycerol are mixed in a mass ratio of 70:15:3, and melt-extrusion blow molding is performed to form an outer film layer with a thickness of 50 μm and an inner film layer with a thickness of 30 μm; Step 2: Mix phase change capsules and polyurethane adhesive in a mass ratio of 0.3:1, add 0.05% BYK-141 defoamer and 10% silica aerogel (pore size of 20-60nm, specific surface area of ​​500-800m² / g) to the resulting mixture, mix well, and apply it on the surface of the aluminum foil layer. After drying, the insulation layer is obtained. The phase change capsules use a mixture of n-octadecane and paraffin as the core material and gum arabic as the wall material, and the outer surface of the wall material is coated with a stearic acid film layer. Step 3: Hot-press the insulation layer and the outer film layer, and adhere the inner film layer to the aluminum foil layer using a polyurethane adhesive (adhesive coating amount is 10-20g / m²). Then, electrostatically spray antibacterial liquid on the inner layer of the inner film layer. After drying, the resulting composite material is cut and finally made into packaging bags using high-frequency welding.

[0022] The antibacterial liquid is prepared by mixing microwave-modified beeswax with a dispersion liquid with a volume four times that of the beeswax and a temperature of 70°C; the dispersion liquid is prepared by mixing an ethanol aqueous solution with a volume concentration of 60% and 2% of Tween 80, 50% of a functional additive, and 5% of 3-aminopropyltriethoxysilane by mass.

[0023] The preparation method of the functional additive is: Step 1: Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (1.5-2 times the mass of chitosan) to the chitosan solution, mix well, adjust the pH to 8.5, and react at 60° C. for 12 hours; then dialyze and freeze-dry the resulting components to obtain a modifier; Step 2: The amino titanium dioxide aerogel is uniformly dispersed in a phosphate buffer solution with a pH of 7.4 at a concentration of 3wt%, and a glutaraldehyde aqueous solution with a mass of 2% and a concentration of 25wt% of the amino titanium dioxide aerogel is added. After stirring at 30°C for 5h, a modifier with a mass of 0.2 times that of the amino titanium dioxide aerogel is added. After reacting at 50°C for 12h, the reaction product is centrifuged and freeze-dried to obtain a functional additive.

[0024] The preparation method of aminated titanium dioxide aerogel is as follows: titanium dioxide aerogel is uniformly dispersed in an ethanol aqueous solution with a volume concentration of 80% at a dosage ratio of 30g / L, and then a silane coupling agent KH-550 is added with a mass of 30% of the titanium dioxide aerogel. After reflux reaction for 4 hours, the reaction product is centrifuged, washed and dried in sequence to obtain the obtained product.

[0025] The preparation method of titanium dioxide aerogel is as follows: 10g / L lauryltrimethylammonium bromide aqueous solution is mixed with 25wt% ammonia water and mesitylene in a volume ratio of 500:1:5, and the mixture is stirred at 500r / min at a temperature of 25°C for 5 hours; then, tetrabutyl titanate with an equal volume to mesitylene is added dropwise to the obtained mixture, and the mixture is stirred at 30°C for 30 hours; after the reaction is completed, the obtained reaction product is gelled at 50°C for 15 hours, and then calcined at 480°C for 2 hours and ball-milled to obtain mesoporous nano-titanium dioxide aerogel (particle size of 200-500 nm and specific surface area of ​​80-120 m² / g).

[0026] The chitosan solution was prepared by adding acetic acid to a chitosan aqueous solution and stirring at 40° C. for 2 h to obtain the chitosan solution; wherein the feed ratio of chitosan, water, and acetic acid was 2 g:100 mL:1 mL.

[0027] The thickness of the aluminum foil layer and the insulation layer in step 2 are 10 μm and 0.8 mm respectively; the coating amount is 100 g / m 2 , the drying temperature is 60℃.

[0028] The preparation method of phase change capsules is as follows: n-octadecane and paraffin are mixed in a mass ratio of 2:1 and heated until completely melted, and then cooled to room temperature as a core material; gum arabic is dissolved in deionized water with a mass 20 times that of the gum arabic and a temperature of 50°C to prepare a wall material solution; the core material and the wall material solution are mixed and the pH is adjusted to 4, and the reaction is stirred at 50°C for 5 hours; after the reaction is completed, the reaction product is cooled, centrifuged, washed and dried in sequence; finally, a layer of stearic acid is melt-coated on the surface of the obtained solid material with a particle size of 8 μm, and the phase change capsule is obtained after cooling and solidification.

[0029] The preparation method of microwave-modified beeswax is as follows: beeswax is irradiated 4 times in an intermittent irradiation mode at a microwave power of 500 W, with each treatment time being 40 seconds.

[0030] The hot pressing temperature during hot pressing and laminating in step 3 is 110° C., the pressure is 0.5 MPa, and the hot pressing time is 30 s.

[0031] Example 2 The preparation method of the food insulation and environmentally friendly express packaging bag provided in this embodiment is basically the same as that in Example 1, except that the specific preparation methods of the antibacterial liquid and functional additives used are different. The specific preparation methods of the antibacterial liquid and functional additives in this embodiment are as follows: The antibacterial liquid is prepared by mixing microwave-modified beeswax with a dispersion liquid with a volume 5 times that of the beeswax and a temperature of 75°C; the dispersion liquid is prepared by mixing an ethanol aqueous solution with a volume concentration of 70% and 3% of Tween 80, 55% of a functional additive, and 6% of 3-aminopropyltriethoxysilane by weight.

[0032] The preparation method of the functional additive is: Step 1: Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (2 times the mass of chitosan) to the chitosan solution, mix well, adjust the pH to 9, and react at 70°C for 10 hours; then dialyze and freeze-dry the resulting components to obtain a modifier; Step 2: The amino titanium dioxide aerogel is uniformly dispersed in a phosphate buffer solution with a pH of 7.4 at a concentration of 5wt%, and a glutaraldehyde aqueous solution with a mass of 25wt% and a concentration of 2.5% of the amino titanium dioxide aerogel is added. After stirring at 35°C for 4 hours, a modifier with a mass of 0.3 times that of the amino titanium dioxide aerogel is added. After reacting at 55°C for 10 hours, the reaction product is centrifuged and freeze-dried to obtain a functional additive.

[0033] Example 3 The preparation method of the food insulation and environmentally friendly express packaging bag provided in this embodiment is basically the same as that in Example 1, except that the specific preparation methods of the antibacterial liquid and functional additives used are different. The specific preparation methods of the antibacterial liquid and functional additives in this embodiment are as follows: The antibacterial liquid is prepared by mixing microwave-modified beeswax with a dispersion liquid with a volume six times that of the beeswax and a temperature of 75°C; the dispersion liquid is prepared by mixing an ethanol aqueous solution with a volume concentration of 80% and 4% of Tween 80, 60% of a functional additive, and 8% of 3-aminopropyltriethoxysilane by mass.

[0034] The preparation method of the functional additive is: Step 1: Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (1.5-2 times the mass of chitosan) to the chitosan solution, mix well, adjust the pH to 9.5, and react at 80° C. for 8 hours; then dialyze and freeze-dry the resulting components to obtain a modifier; Step 2: The amino titanium dioxide aerogel is uniformly dispersed in a phosphate buffer solution with a pH of 7.4 at a concentration of 6wt%, and a glutaraldehyde aqueous solution with a mass of 3% and a concentration of 25wt% of the amino titanium dioxide aerogel is added. After stirring at 40°C for 3 hours, a modifier with a mass of 0.4 times that of the amino titanium dioxide aerogel is added. After reacting at 60°C for 8 hours, the reaction product is centrifuged and freeze-dried to obtain a functional additive.

[0035] The preparation method of aminated titanium dioxide aerogel is as follows: titanium dioxide aerogel is uniformly dispersed in an ethanol aqueous solution with a volume concentration of 90% at a dosage ratio of 80g / L, and then a silane coupling agent KH-550 with a mass of 40% of the titanium dioxide aerogel is added. After reflux reaction for 6 hours, the reaction product is centrifuged, washed and dried in sequence to obtain the obtained product.

[0036] The preparation method of titanium dioxide aerogel is as follows: 20g / L lauryltrimethylammonium bromide aqueous solution is mixed with ammonia water and mesitylene in a volume ratio of 800:1:10, and the mixture is stirred at 1000r / min at a temperature of 35°C for 3 hours; then, tetrabutyl titanate with an equal volume to mesitylene is added dropwise to the obtained mixture, and the mixture is stirred and reacted at 40°C for 20 hours; after the reaction is completed, the obtained reaction product is gelled at 60°C for 10 hours, and then calcined and ball-milled to obtain titanium dioxide aerogel.

[0037] Comparative Example 1 is different from Example 1 in that silica aerogel is used in the insulation layer of this comparative example instead of an equal amount of phase change capsules.

[0038] Comparative Example 2 is different from Example 1 in that titanium dioxide aerogel is used in this comparative example to replace an equal amount of functional additives.

[0039] Comparative Example 3 is different from Example 1 in that titanium dioxide of the same specifications (particle size of 200-500 nm) is used in this comparative example to replace the same amount of functional additives.

[0040] Comparative Example 4 is different from Example 1 in that the propolis used in this comparative example has not been microwave-modified.

[0041] Performance testing: The relevant properties of the express packaging bag samples prepared in Examples 1-3 and Comparative Examples 1-4 were tested as follows: 1. Thermal insulation performance test: Pour 60℃ distilled water into the food insulation environmentally friendly express packaging bag, and then place it in a constant temperature box at 25℃. Measure the temperature of the distilled water in the bag after 1 hour and 3 hours.

[0042] 2. Antibacterial performance: Tested in accordance with GB / T 31402-2015 "Test method for antibacterial properties of plastic surfaces".

[0043] 3. Degradation performance test: The test is conducted in accordance with GB / T 19277.1-2011 "Test method for biodegradability of compostable materials"; the test conditions are: composting environment at 58±2℃, and the mass loss rate is measured after 180 days. The reason why Example 1 has better antibacterial performance than Comparative Example 1 may be related to the high porosity and large specific surface area of ​​silica aerogel. This nanoporous structure may inhibit bacterial growth by physical adsorption or destruction of bacterial cell membranes, but the effect is relatively weak.

[0044] The higher degradation rate of the express packaging bag prepared in Comparative Example 1 than in Example 1 may be due to the fact that silica aerogel is an inorganic material primarily composed of silica, and its degradation relies on physical disintegration rather than biodegradation. However, through the synergistic effect of polylactic acid and chitosan, its overall degradability can drive the dispersion and mineralization of the aerogel through the degradation of its organic components. While the wall material of the phase change capsule is degradable, the degradation cycle of its core material is much longer than that of silica aerogel.

[0045] The weaker antibacterial performance of Comparative Example 4 compared to Example 1 also indirectly supports the fact that microwave-modified beeswax improves its antibacterial properties. Furthermore, since microwave-modified beeswax partially breaks its ester bonds, it produces more short-chain fatty acids (such as palmitic acid and propolis acid) and free alcohols, effectively shortening its degradation cycle and increasing its degradation rate.

[0046] Comparing and analyzing the relevant data in the table shows that the express shipping packaging bags prepared by the present invention not only have excellent thermal insulation and antibacterial properties, but also have good biodegradability, are relatively environmentally friendly, and can meet the multiple packaging requirements of modern food logistics. This shows that the method for preparing the insulated and environmentally friendly express shipping packaging bags for food provided by the present invention has a broader market prospect and is more suitable for promotion.

[0047] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0048] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a food insulation and environmentally friendly express packaging bag, characterized in that: The following steps are involved: Step 1: polylactic acid, carboxymethyl starch and glycerol are mixed in a mass ratio of 70-85:15-30:3-8, and melt-extrusion blow molding is performed to form an outer film layer with a thickness of 50-100 μm and an inner film layer with a thickness of 30-80 μm; Step 2: Mixing phase change capsules with polyurethane adhesive in a mass ratio of 0.3-0.6:1, adding 0.05-1% by weight of a defoamer and 10-15% by weight of a silica aerogel to the resulting mixture, mixing well, and coating the mixture on the surface of the aluminum foil layer. After drying, the insulation layer is obtained. The phase change capsules have a core material of a mixture of n-octadecane and paraffin wax, a wall material of gum arabic, and an outer surface of the wall material coated with a stearic acid film layer. Step 3: Hot-press the insulation layer and the outer film layer, adhere the inner film layer to the aluminum foil layer with a polyurethane adhesive, then electrostatically spray antibacterial liquid on the inner layer of the inner film layer, cut the resulting composite material after drying, and finally use high-frequency welding to make packaging bags.

2. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 1, characterized in that: The antibacterial liquid is prepared by mixing microwave-modified beeswax with a dispersion liquid with a volume 4-6 times that of the beeswax and a temperature of 70-75°C; wherein the dispersion liquid is prepared by mixing an ethanol aqueous solution with a volume concentration of 60-80% and Tween 80 with a mass concentration of 2-4% of the beeswax, a functional additive of 50-60%, and 3-aminopropyltriethoxysilane with a mass concentration of 5-8%.

3. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 2, characterized in that: The preparation method of the functional additive is: Step 1: Add 3-chloro-2-hydroxypropyltrimethylammonium chloride (1.5-2 times the mass of chitosan) to the chitosan solution, mix well, adjust the pH to 8.5-9.5, and react at 60-80° C. for 8-12 hours; then dialyze and freeze-dry the resulting components to obtain a modifier; Step 2: The amino titanium dioxide aerogel is uniformly dispersed in a phosphate buffer solution with a pH of 7.4 at a concentration of 3-6wt%, and a glutaraldehyde aqueous solution with a mass of 2-3% and a concentration of 25wt% of the amino titanium dioxide aerogel is added. After stirring at 30-40°C for 3-5h, a modifier with a mass of 0.2-0.4 times that of the amino titanium dioxide aerogel is added. After reacting at 50-60°C for 8-12h, the reaction product is centrifuged and freeze-dried to obtain a functional additive.

4. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 3, characterized in that: The preparation method of the amino-treated titanium dioxide aerogel comprises the following steps: uniformly dispersing the titanium dioxide aerogel in an ethanol aqueous solution with a volume concentration of 80-90% at a dosage ratio of 30-80 g / L, then adding a silane coupling agent KH-550 in an amount of 30-40% by mass of the titanium dioxide aerogel, and subjecting the reaction to reflux reaction for 4-6 hours, followed by centrifugal washing and drying of the reaction product.

5. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 4, characterized in that: The preparation method of titanium dioxide aerogel comprises the following steps: mixing a 10-20 g / L lauryltrimethylammonium bromide aqueous solution with ammonia water and mesitylene in a volume ratio of 500-800:1:5-10, and stirring the mixture at a temperature of 25-35° C. and a speed of 500-1000 r / min for 3-5 hours; then, adding tetrabutyl titanate having an equal volume to that of mesitylene dropwise to the obtained mixture, and stirring the mixture at 30-40° C. for 20-30 hours; and after the reaction is completed, gelling the obtained reaction product at 50-60° C. for 10-15 hours, and then calcining and ball milling the mixture to obtain titanium dioxide aerogel.

6. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 3, characterized in that: The chitosan solution is prepared by adding acetic acid to a chitosan aqueous solution and stirring at 40-60° C. for 1-2 hours to obtain the chitosan solution; wherein the feed ratio of chitosan, water, and acetic acid is 2-5 g:100 mL:1-2.5 mL.

7. The method for preparing a heat-insulating, environment-friendly, express delivery food packaging bag according to claim 1, characterized in that: The thickness of the aluminum foil layer and the insulation layer in step 2 are 10-50 μm and 0.8-1.2 mm respectively; the coating amount is 100-180 g / m 2 , the drying temperature is 60-90℃.

8. The method for preparing a food heat-insulating and environment-friendly express packaging bag according to claim 1, characterized in that: The preparation method of the phase-change capsules comprises the following steps: mixing n-octadecane and paraffin wax in a mass ratio of 2-4:1, heating the mixture until completely melted, and cooling the mixture to room temperature to prepare a core material; dissolving gum arabic in deionized water having a mass of 20-50 times that of the mixture and a temperature of 50-60°C to prepare a wall material solution; mixing the core material and the wall material solution, adjusting the pH to 4-4.5, and stirring the mixture at 50-60°C for 3-5 hours; after the reaction is complete, sequentially cooling, centrifuging, washing, and drying the reaction product; and finally melt-coating a layer of stearic acid on the surface of the obtained solid material having a particle size of 8-12 μm, followed by solidification through cooling to obtain the phase-change capsules.

9. The method for preparing a heat-insulating, environmentally friendly, express delivery packaging bag for food according to claim 2, characterized in that: The preparation method of the microwave-modified beeswax comprises the following steps: irradiating the beeswax 2-4 times in an intermittent irradiation mode at a microwave power of 500-1000 W, with each treatment time being 20-40 seconds.

10. The method for preparing a heat-insulating and environment-friendly food express packaging bag according to claim 1, characterized in that: During the hot pressing and laminating in step 3, the hot pressing temperature is 110-150° C., the pressure is 0.5-3 MPa, and the hot pressing time is 10-30 seconds.

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