Breathable and environment-friendly fruit and vegetable fresh-keeping bag and preparation method thereof

Abstract

The invention discloses a breathable and environment-friendly fruit and vegetable fresh-keeping bag and a preparation method thereof, and relates to the technical field of packaging bags, and the fruit and vegetable fresh-keeping bag is composed of composite plastic and graphene; the graphene is nano graphene; the average particle size is 100 nm; the fruit and vegetable fresh-keeping bag is prepared from the following components in percentage by weight: 1 to 3 percent of graphene and 97 to 99 percent of composite plastic, the composite plastic is prepared from poly (butylene succinate), polylactic acid and clay. Wherein the clay is nano clay, and the clay comprises small-particle-size clay and large-particle-size clay; the particle size of the small-particle-size clay is 50nm, and the particle size of the large-particle-size clay is 100-200nm; the clay comprises montmorillonite; compared with the prior art, the high-carbon-dioxide-permeability graphene film has the advantages that higher carbon dioxide permeability can be achieved, the effective performance of graphene is protected in a high-humidity environment, long-time effective action is achieved, and deterioration of fruits and vegetables caused by too high carbon dioxide concentration can be prevented for fruits and vegetables with strong respiration.

Description

Technical Field

[0001] The invention relates to the technical field of packaging bags, and in particular to a breathable and environment-friendly fruit and vegetable fresh-keeping bag and a preparation method thereof. Background Art

[0002] Fresh and perishable agricultural products have extremely high requirements for preservation technology. Their easy rot and deterioration after harvest leads to a high loss rate in the post-harvest transportation and sales links, which seriously restricts the development of the industry. Although traditional preservation methods such as low-temperature refrigeration can delay metabolism, it is difficult to meet the needs of long-distance transportation and shelf life preservation. The use of modified atmosphere packaging technology has become a key means to extend the shelf life by effectively inhibiting respiration and microbial reproduction by adjusting the gas environment in the package.

[0003] For example, the Chinese patent application number CN202011167412.6 is a kind of controlled atmosphere fresh-keeping bag for fruits and vegetables, and its preparation method and application. The controlled atmosphere fresh-keeping bag for fruits and vegetables is mainly composed of polyethylene and graphene. By adding graphene to polyethylene, on the one hand, the strength of the fresh-keeping bag can be improved, and on the other hand, the pores of the fresh-keeping bag can be changed, so that it has the ability to adjust the oxygen and carbon dioxide content in both directions, ensuring that the humidity in the bag is appropriate, and effectively adjusting the gas index to achieve the effect of controlled atmosphere preservation. After 20 days of preservation at low temperature, the good fruit rate of lychees can reach more than 95%. In addition, the preparation method of the controlled atmosphere fresh-keeping bag for fruits and vegetables is simple and convenient for industrial production.

[0004] However, by only adding graphene as a nucleating agent, the crystallinity of the plastic material is increased, the free volume of the amorphous region is reduced, and the diffusion rate of carbon dioxide is also inhibited, which can easily lead to the accumulation of carbon dioxide in the bag and poison the fruits and vegetables. Moreover, under high humidity conditions, water molecules penetrate into the graphene layers, destroying its original structural order and reducing its stability, which can easily lead to the failure of the two-way regulation and ultimately the loss of the preservation effect. Summary of the invention

[0005] The embodiment of the present application solves the problem of damage to the stability of graphene caused by high humidity environment in the prior art by providing a breathable and environmentally friendly fruit and vegetable fresh-keeping bag and a preparation method thereof, thereby achieving a long-term preservation effect.

[0006] The embodiment of the present application provides a breathable and environmentally friendly fruit and vegetable fresh-keeping bag, wherein the fruit and vegetable fresh-keeping bag is composed of composite plastic and graphene; the graphene is nanographene; and the average particle size is 100 nm; The fruit and vegetable fresh-keeping bag is composed of the following components in percentage by weight: 1-3% graphene and 97-99% composite plastic; The composite plastic is composed of polybutylene succinate, polylactic acid and clay; Among them, the clay is nano clay, including montmorillonite, and the clay includes small-particle clay and large-particle clay; the particle size of the small-particle clay is 50nm, and the particle size of the large-particle clay is 100-200nm.

[0007] Furthermore, in the composite plastic, the polybutylene succinate and polylactic acid together account for 94%-98% of the total weight of the composite plastic; and the mass of clay accounts for 1-3% of the total weight of the composite plastic.

[0008] Furthermore, the mass ratio of polybutylene succinate:polylactic acid is 7:3.

[0009] Furthermore, the mass ratio of the small-size clay to the large-size clay is 2:1.

[0010] Furthermore, clay is divided into tubular clay and flaky clay.

[0011] Furthermore, tubular clay is composed of clay particles and AlCl 3 6H 2 O is prepared; the specific preparation process is: clay particles are used as silicon source, AlCl 3 6H 2 O as aluminum source, mixed in a silicon: aluminum molar ratio of 1:1, the mixture was dispersed in water, and the slurry concentration was adjusted to 10wt%; reacted at 180℃ for 48h, centrifuged, washed, dried, and then stirred at 60℃ for 2h in 1mol / L HCl to remove unreacted montmorillonite, and then calcined at high temperature to obtain a crude tubular clay; The crude tubular clay was dispersed in toluene, 3-aminopropyltriethoxysilane was added, triethylamine was used as a catalyst, and the mixture was stirred at 80° C. for 24 hours under a nitrogen atmosphere; the mixture was washed with ethanol and deionized water in sequence, and vacuum dried at 50° C. to obtain tubular clay.

[0012] Furthermore, the fresh-keeping bag has a double-layer film, which is a laminated composite double-layer film. The inner and outer layers of the double-layer film have different structures, and carbon dioxide gas is filled in the middle.

[0013] Furthermore, the outer layer adopts a combination of resin + graphene + flaky clay, and the inner layer adopts a combination of resin + graphene + tubular clay. Carbon dioxide gas is filled between the two layers, and the concentration of carbon dioxide in the filled gas is 10-20%.

[0014] The preparation method of the above-mentioned breathable and environmentally friendly fruit and vegetable fresh-keeping bag comprises the following steps: S1. Mix the composite plastic and graphene in a high-speed disperser, and then put them into a twin-screw granulator, and make them into granules after passing through temperature zones of 130° C., 140° C., 150° C., and 160° C. in sequence; S2. The particles are extruded through an extruder at 160-170°C, and then film-formed through blow molding, cooling, clamping, pulling, and rolling processes in sequence, and finally made into fruit and vegetable fresh-keeping bags with specifications of 43cm×38.1cm×10μm.

[0015] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: First, the key to preserving fruits and vegetables is low oxygen and high carbon dioxide, but too high carbon dioxide can also be harmful, so it is necessary to reduce oxygen as much as possible and maintain an appropriate carbon dioxide concentration; by using a combination of graphene and clay; reducing the permeability of oxygen, increasing the permeability of carbon dioxide, and improving the moisture stability of graphene.

[0016] Second, the combination of small-particle clay and large-particle clay can form a combined effect of small-particle adsorption and large-particle transport, which not only complicates the barrier network but also increases the resistance to CO 2 Transfer capacity.

[0017] Third, by preparing the clay particles into tubular clay particles and performing an amination treatment, the adsorption capacity is greatly improved, the water retention capacity is improved, the diffusion path is optimized, and the circulation stability is increased.

[0018] Fourth, through the multi-layer combination, the outer layer is oxygen-blocking and the inner layer is CO permeable 2 , combined with initial aeration to quickly establish a low-oxygen environment, synergistically control humidity, and reduce the risk of water loss and mildew of fruits and vegetables. DETAILED DESCRIPTION

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items.

[0020] Embodiment 1: The present application provides a breathable and environmentally friendly fruit and vegetable preservation bag, wherein the fruit and vegetable preservation bag is composed of composite plastic and graphene; The graphene is nanographene with an average particle size of 100 nm; The composite plastic is composed of polybutylene succinate (PBS), polylactic acid (PLA) and clay; The clay is nanoclay with a particle size of 50-200nm; the clay includes montmorillonite; The fruit and vegetable fresh-keeping bag is composed of the following components in percentage by weight: 1-3% graphene and 97-99% composite plastic; The PBS and PLA in the composite plastic together account for 94%-98% of the total weight of the composite plastic; the mass ratio of PBS:PLA is 7:3, and the mass of clay accounts for 1-3% of the total weight of the composite plastic; The preparation method of the fruit and vegetable fresh-keeping bag comprises the following steps: S1. Mix the composite plastic and graphene in a high-speed disperser, and then put them into a twin-screw granulator, and make them into granules after passing through temperature zones of 130° C., 140° C., 150° C., and 160° C. in sequence; S2. The particles are extruded through an extruder at 160-170° C., and then film-formed through blow molding, cooling, clamping, pulling, and rolling processes in sequence, and finally made into fruit and vegetable fresh-keeping bags with specifications of 43 cm×38.1 cm×10 μm (length, width, thickness).

[0021] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: The key to preserving fruits and vegetables is low oxygen and high carbon dioxide, but too much carbon dioxide can also be harmful, so it is necessary to reduce the oxygen concentration as much as possible and maintain an appropriate carbon dioxide concentration; By using graphene and clay in combination; reducing the permeability of oxygen, increasing the permeability of carbon dioxide, and improving the moisture stability of graphene; The structure of graphene has a nanosheet barrier effect, and O 2 The molecules are small and non-polar, and they rely more on the free volume diffusion path. The graphene sheet hinders them more significantly, reducing the O 2 The graphene surface contains a small amount of oxygen-containing groups, which form a micro-region polar interface with the non-polar segments of PBS and preferentially adsorb CO 2 and water molecules, thereby selectively capturing and releasing CO 2 , and finally a dynamic equilibrium is formed. Graphene reduces the free volume of the amorphous region, further inhibiting gas diffusion; while CO 2 The polarity of O allows it to diffuse through the interface region, and the permeability decrease is less than that of O 2 , less affected; Clay is a layered silicate with a rich surface of polar hydroxyl groups (-OH), which together with graphene form a multi-level barrier network. It has the same effect as graphene in terms of oxygen barrier and carbon dioxide permeation. It can also form a gradient interface with the polarity difference of graphene, enhancing the CO 2 affinity to O 2 The high barrier property of O is achieved through the gradient design of polar interface (clay) and non-polar layer (graphene). 2 / CO 2 The reverse regulation of permeability is suitable for the preservation of fruits and vegetables with high respiration intensity; The combination of graphene and clay forms a three-dimensional porous structure, which can prevent the shrinkage of pores and the leakage of liquid substances, and also gives the material excellent adsorption properties. As the clay content increases, the surface of the mixed material becomes rougher and rougher, but the overall stability of the porous structure is maintained, and it still has good structural stability in multiple high-humidity cold-heat cycle experiments; PBS is a biodegradable plastic material with good toughness and degradability. It can be decomposed into harmless substances in the natural environment, providing flexibility and tensile strength. PLA is a biodegradable plastic made from renewable plant materials, which increases stiffness and hardness. PBS and PLA have good complementarity. The addition of PBS can improve the flexibility and impact strength of PLA, making it more suitable for application areas such as packaging materials and single-use products. The addition of PLA can improve the rigidity and processing properties of PBS and enhance the overall performance of the material. Clay can provide attachment points for microorganisms in the environment of soil degradation, promote biodegradation, and the non-polar chain segments of PBS form micro-area dispersion with the polar interface of clay to inhibit agglomeration.

[0022] The fresh-keeping bag material prepared in Example 1 was measured using a gas permeameter (ASTM D1434 standard) at 25°C. 2 and CO 2 The permeability of the results are shown in Table 1 and Table 2; The temperature / humidity combined cycle test was carried out according to GB / T 2423.34. The high temperature stage (2h) of the temperature cycle was 60℃, 95% humidity, the low temperature stage (1h) was -10℃, the cooling rate was 1.5℃ / min, and the cycle was repeated 10 times. The results are shown in Table 3. Table 1 ; Table 2 ; Table 3 ; The combination of graphene and clay increases the permeability to carbon dioxide and reduces the permeability of oxygen, which can reduce the accumulation of carbon dioxide in the packaging bag environment and further prevent oxygen from entering and aerobic respiration, which is beneficial for packaging fruits and vegetables with high respiration intensity. Temperature and humidity cycles cause partial relaxation of the amorphous region and a slight increase in free volume, but the graphene-clay network still effectively inhibits gas diffusion.

[0023] Example 2: The above example uses degradable plastic and combines it with clay and graphene to obtain a degradable, moisture-resistant fruit and vegetable packaging bag. For the process of differentiation, adsorption and transport, the clay particles are divided into different parts, which is further improved on the basis of Example 1.

[0024] The clay includes small-size clay and large-size clay; the particle size of the small-size clay is 50nm, the particle size of the large-size clay is 200nm, and the mass ratio of the small-size clay to the large-size clay is 2:1.

[0025] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: The combination of small-size clay and large-size clay can form a combined effect of small-size adsorption and large-size transport, which complicates the barrier network and increases the resistance to CO 2 Transshipment capacity; Small-particle clays are rich in hydroxyl groups (-OH) and cations on their surfaces, which preferentially capture CO through polar adsorption and hydrogen bonding. 2 molecules, forming local high concentration areas, and uneven charge distribution on the surface of small-sized clay particles, which enhances the 2 The small-sized clay particles are also easily adsorbed around the large-sized clay particles to form CO 2 Agglomerate around small-sized particles, and small-sized particles agglomerate around large-sized particles; large-sized particles form a structure with enlarged interlayer spacing through intercalation or exfoliation, which is CO 2 Provide a fast diffusion path, reduce diffusion resistance, fill the amorphous area of ​​the matrix, reduce free volume, and inhibit O 2 The combination of the two allows small-particle clay to adsorb CO 2 , and then transported and diffused through the large-particle clay, and the hydrophobic surface of graphene formed a dynamic CO interface with the polar interface of the small-particle clay. 2 transmission chain, further optimizing CO 2 transportation route.

[0026] While small-sized particles agglomerate around large-sized particles, they compete with graphene for the adsorption of water molecules. The adsorption capacity of interlayer cations of clay is stronger than that of graphene (especially small-sized clay). While increasing the adsorption of water molecules, it also increases the polarity, which increases the adsorption capacity of carbon dioxide. During the extrusion blow molding process, the clay flakes are oriented along the flow direction to form a layered barrier structure. The clay flakes are evenly dispersed in the matrix (especially large-sized clay), wrapping the graphene in the "pocket", blocking the water penetration path and reducing the contact between graphene and water molecules. During the cooling process, the clay and the plastic matrix shrink synchronously, closing the residual pores and improving the moisture resistance of graphene.

[0027] The plastic material prepared in Example 2 was tested for O 2 and CO 2 The permeability of the results is shown in Table 4; The temperature / humidity combined cycle test was carried out according to GB / T 2423.34. The high temperature stage (2h) of the temperature cycle was 60℃, 95% humidity, the low temperature stage (1h) was -10℃, the cooling rate was 1.5℃ / min, and the cycle was repeated 10 times. The results are shown in Table 5. Table 4 ; Table 5 ; Example 3: Example 2 not only increases the adsorption and transport capacity of carbon dioxide by combining clays of different particle sizes, taking into account both adsorption capacity and channel continuity, but also further improves the stability of graphene under high humidity conditions. Further improvements are made to improve the spacing between clay layers and optimize the transmission path.

[0028] The tubular clay is obtained by modifying the clay and then performing amination, specifically: Montmorillonite is used as silicon source, AlCl 3 6H 2 O as aluminum source, mixed in a silicon: aluminum molar ratio of 1:1, the mixture was dispersed in water, and the slurry concentration was adjusted to 10wt%; reacted at 180℃ for 48h, centrifuged, washed, dried, and then stirred at 60℃ for 2h in 1mol / L HCl to remove unreacted montmorillonite, and then calcined at high temperature (500℃ / 2h) to obtain a crude tubular clay; The crude tubular clay was dispersed in toluene, 3-aminopropyltriethoxysilane was added, triethylamine was used as a catalyst, and the mixture was stirred at 80° C. for 24 hours under a nitrogen atmosphere; the mixture was washed with ethanol and deionized water in sequence, and vacuum dried at 50° C. to obtain tubular clay.

[0029] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: By preparing the clay particles into tubular clay particles and performing an amination treatment, the adsorption capacity is greatly improved, the water retention capacity is improved, the diffusion path is optimized, and the circulation stability is increased.

[0030] Montmorillonite is a flaky clay that forms a dense barrier network. 2 The barrier property is strong, but it is not suitable for CO 2 The adsorption and transport effect of CO is limited. By preparing tubular clay particles with hollow tubes (diameter 20-50 nm, length 200-1000 nm), directional channels are formed. 2 Rapid diffusion along the lumen can greatly increase the permeability and increase CO 2 The diffusion rate of molecules in the nanotubes is then further increased through amino modification to further increase its adsorption capacity for carbon dioxide. Small-sized tubular clay has high surface energy and strong water absorption capacity. After agglomerating on the surface of large-sized tubular clay particles, the agglomerates form a core-shell structure, the outer layer is densified, and the internal pores inhibit liquid water penetration due to the capillary effect, which can prevent water molecules from seeping out and reduce the contact area between water molecules and graphene. Small-sized tubular clay particles tend to entangle and agglomerate, reducing CO 2The transfer efficiency is improved, but the degree of bonding between graphene and the aminated tubular clay increases. The flake graphene is easier to insert into the gaps of the agglomerated tubular clay, preventing agglomeration through steric hindrance. In addition, graphene has a hydrophobic surface, which can reduce the interfacial energy of the mixed system and reduce the driving force for agglomeration. The sp 2 The hybrid carbon network can form a weak interaction with the oxygen atoms of the silicon-oxygen tetrahedron layer on the outer surface of the tubular clay, increasing the adsorption capacity. The addition of graphene reduces the viscosity of the dispersed system, improves fluidity, and inhibits the formation of agglomerates. The plastic material prepared in Example 3 was measured using a gas permeameter (ASTM D1434 standard) at 25°C. 2 and CO 2 The permeability is shown in Table 6; wherein the tubular clay is the aminated tubular clay after the multi-particle size combination group in Example 2 is modified into a tubular shape and aminated; the flaky clay is the clay of the multi-particle size combination used in Example 2; The temperature / humidity combined cycle test was carried out according to GB / T 2423.34. The high temperature stage (2h) of the temperature cycle was 60℃, 95% humidity, the low temperature stage (1h) was -10℃, the cooling rate was 1.5℃ / min, and the cycle was repeated 10 times. The results are shown in Table 7. Table 6 ; Table 7 ; Embodiment 4: Embodiment 3 uses tubular clay to greatly enhance the transport capacity of carbon dioxide, and further improves the structure of the plastic fresh-keeping bag on the basis of Embodiment 3 to optimize the whole.

[0031] Fresh-keeping bags have double-layer film; The double-layer membrane is a laminated double-layer membrane with different inner and outer layer structures, specifically: The outer layer adopts a combination of resin + graphene + flaky clay, and the inner layer adopts a combination of resin + graphene + tubular clay. Carbon dioxide gas is filled between the two layers, and the concentration of carbon dioxide in the filled gas is 10-20% (this concentration is the concentration of carbon dioxide in the filled gas).

[0032] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages: Through multi-layer combination, the outer layer blocks oxygen and the inner layer allows CO to pass through 2 , combined with initial aeration to quickly establish a low-oxygen environment, synergistically control humidity, and reduce the risk of water loss and mildew of fruits and vegetables.

[0033] The flaky clay and graphene form a dense network, which significantly reduces the oxygen permeability, blocks the entry of external oxygen, and also reduces the penetration of external water vapor, keeping the humidity in the bag stable; the hollow channels and amino modification of the tubular clay enhance the adsorption and diffusion capacity of carbon dioxide, add carbon dioxide gas in the interlayer, and use the concentration difference to control the concentration of carbon dioxide in the bag. After a large amount of carbon dioxide is produced, the CO2 in the bag is promoted. 2 The polar surface of the tubular clay absorbs water molecules to reduce water loss in fruits and vegetables, which not only ensures the humidity of fruits and vegetables to prevent water loss, but also protects graphene to prevent its function from being reduced due to high humidity. When fruits and vegetables are just put into the bag, the inflation can also directly reduce the O 2 concentration, inhibiting aerobic respiration of fruits and vegetables and reducing metabolic consumption.

[0034] Take apples as an example. In an environment with low oxygen content, the anaerobic respiration of apples is still strong, producing carbon dioxide and alcohol. In a moisturizing state, the peak of respiration is delayed, which is conducive to reducing respiration. The fruit and vegetable belts prepared in Example 4 were tested for their preservation effect, specifically: apples of the same batch collected from Yantai, Shandong Province, which were not damaged and had good appearance, were placed in fruit and vegetable preservation bags (two per bag), the bags were tied tightly and stored at 1-3°C, and the browning rate and good fruit rate were measured after 100 days; the results are shown in Table 8; Table 8 ; The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag, characterized in that: The fruit and vegetable fresh-keeping bag is composed of composite plastic and graphene; the graphene is nanographene; the average particle size is 100nm; The fruit and vegetable fresh-keeping bag is composed of the following components in percentage by weight: 1-3% graphene and 97-99% composite plastic; The composite plastic is composed of polybutylene succinate, polylactic acid and clay; Among them, the clay is nano clay, including montmorillonite, and the clay includes small-particle clay and large-particle clay; the particle size of the small-particle clay is 50nm, and the particle size of the large-particle clay is 100-200nm.

2. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 1, characterized in that: In the composite plastic, the polybutylene succinate and polylactic acid together account for 94%-98% of the total weight of the composite plastic; and the mass of clay accounts for 1-3% of the total weight of the composite plastic.

3. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 2, characterized in that: The mass ratio of polybutylene succinate:polylactic acid is 7:

3.

4. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 1, characterized in that: The mass ratio of small-size clay to large-size clay is 2:

1.

5. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 4, characterized in that: Clay is divided into tubular clay and flaky clay.

6. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 5, characterized in that: The tubular clay is prepared from clay particles and AlCl3·6H2O. The specific preparation process is as follows: clay particles are used as silicon source and AlCl3·6H2O is used as aluminum source, mixed in a silicon:aluminum molar ratio of 1:1, the mixture is dispersed in water, and the slurry concentration is adjusted to 10wt%; reacted at 180°C for 48h, centrifuged, washed, dried, and then stirred in 1mol / L HCl at 60°C for 2h to remove unreacted montmorillonite, and then calcined at high temperature to obtain a crude tubular clay; The crude tubular clay was dispersed in toluene, 3-aminopropyltriethoxysilane was added, triethylamine was used as a catalyst, and the mixture was stirred at 80° C. for 24 hours under a nitrogen atmosphere; the mixture was washed with ethanol and deionized water in sequence, and vacuum dried at 50° C. to obtain tubular clay.

7. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 6, characterized in that: The fresh-keeping bag has a double-layer film, which uses a laminated composite double-layer film. The inner and outer layers of the double-layer film have different structures and are filled with carbon dioxide gas in the middle.

8. A breathable and environmentally friendly fruit and vegetable fresh-keeping bag as claimed in claim 7, characterized in that: The outer layer uses a combination of resin + graphene + flaky clay, and the inner layer uses a combination of resin + graphene + tubular clay. Carbon dioxide gas is filled between the two layers, and the concentration of carbon dioxide in the filled gas is 10-20%.

9. A method for preparing a breathable and environmentally friendly fruit and vegetable fresh-keeping bag according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1, mixing the composite plastic and graphene in a high-speed disperser, and then putting them into a twin-screw granulator, and then passing through the temperature zones of 130°C, 140°C, 150°C, and 160°C to form granules; S2. The particles are extruded through an extruder at 160-170°C, and then film-formed through blow molding, cooling, clamping, pulling, and rolling processes in sequence, and finally made into fruit and vegetable fresh-keeping bags with specifications of 43cm×38.1cm×10μm.