Porous in-situ microfiber active preservative film and preparation method thereof

Abstract

The invention discloses a porous in-situ microfiber active preservative film and a preparation method thereof, and relates to the technical field of films, and the preparation method comprises the following steps: loading an ethylene elimination agent and / or an antibacterial agent as active substances on a porous framework material to obtain an active substance-porous framework material; the preparation method comprises the following steps: preparing an active substance-porous framework material, blending the active substance-porous framework material and a polymer as a fiber phase, mixing the fiber phase and a matrix phase, carrying out micro-nano lamination co-extrusion to form a composite material, and etching the matrix phase in the composite material with a good solvent to obtain the porous in-situ microfiber active preservative film. According to the invention, the three-dimensional porous network structure of the active preservative film has a controlled atmosphere function and inhibits respiration of fruits and vegetables; under the action of the three-dimensional porous network structure and the porous framework material, active substances in the active preservative film can be slowly and continuously released to play a long-acting antibacterial role and / or ethylene elimination role, so that the preservation period of fruits and vegetables is prolonged to the greatest extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin films, and particularly relates to a porous in-situ microfiber active fresh-keeping film and a preparation method thereof. Background Art

[0002] Inhibiting the senescence of fruits and vegetables includes controlling respiration, timely eliminating ethylene ripening gas, preventing bacterial growth and other ways.

[0003] Electrospinning is a technology with simple operation that can continuously prepare polymer nanofibers. Due to the advantages of high porosity, large specific surface area and easy recycling of the prepared nanofiber membranes, it has been widely used in many research fields. In recent years, its application in functional food packaging has also attracted much attention. According to existing research, it has been found that the butyl caffeate-mediated multifunctional food preservation nanocomposite packaging material made by nano-electrospinning technology not only has good antibacterial and antioxidant properties, but also has edibility, can be used as a carrier for nutrients and functional components, is safe, stable and efficient, and has a wide range of applications. For example, as a multifunctional food preservation material, on the basis of ensuring excellent food preservation function, it will not produce toxic effects on the human body after being eaten and absorbed by people, but can also provide certain nutritional value for the human body; in the field of medical pharmaceuticals, making packaging materials such as capsules can make the content medicaments slowly release in the human body, thereby improving safety, prolonging the drug action time, and thus achieving a better therapeutic effect; in terms of environmental protection, this product belongs to nanomaterials, with natural raw materials, and can be degraded after being treated by nano-electrospinning technology, which is friendly to the environment and organisms, and is green and environmentally friendly.

[0004] An active modified atmosphere fresh-keeping film refers to a film with a modified atmosphere function and added with an ethylene eliminator or an antibacterial agent. For example, in the publicly disclosed patent CN115819819B, a humidity-controlled, rapid oxygen reduction and antibacterial fresh-keeping film for fruits and vegetables and its preparation method and application, the fresh-keeping film is composed of a chitosan / silver-phosphorylated polyether ether ketone antibacterial layer, a micro-nano iron / polyurethane oxygen reduction layer and a polytetrafluoroethylene humidity control layer. The composite film integrates multiple functions such as spontaneous regulation of humidity and gas components, rapid deoxidation and long-term antibacterial properties, and can effectively control the humidity of the storage environment and control the transpiration of fruits and vegetables. However, the long-term effectiveness of the functional additives is difficult to meet the requirements, and there is a need to study fresh-keeping films that can have long-term antibacterial properties and eliminate ethylene. Summary of the Invention

[0005] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0006] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0007] Therefore, an object of the present invention is to overcome the deficiencies in the prior art and provide a porous in-situ microfiber active fresh-keeping film.

[0008] To solve the above technical problems, the present invention provides the following technical solutions:

[0009] The porous in-situ microfiber active fresh-keeping film is a three-dimensional network structure formed by the free stacking of nanofibers, and a porous structure is formed between the nanofibers, and the size of the pore diameter is 10-1000 nm;

[0010] Among them, the nanofibers are composed of a porous skeleton material and polymer B, and an antibacterial agent and / or an ethylene scavenger are loaded on the porous skeleton material;

[0011] The polymer B includes one or more of polylactic acid, polypropylene, polyamide, polyethylene terephthalate, and polybutylene adipate terephthalate; the antibacterial agent includes one or more of quercetin, curcumin, cinnamon essential oil, thymol, and carvacrol.

[0012] Another object of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of a porous in-situ microfiber active fresh-keeping film.

[0013] To solve the above technical problems, the present invention provides the following technical solutions:

[0014] The active substance is loaded on the porous skeleton material to form an active substance-porous skeleton material;

[0015] The active substance-porous skeleton material is melt-blended and pelletized with polymer B to form a fiber phase;

[0016] The fiber phase and the matrix phase are mixed evenly, and an in-situ microfiber composite material is formed by micro-nano layer-by-layer coextrusion;

[0017] The matrix phase in the in-situ microfiber composite material is etched by a solvent to form a porous in-situ microfiber active fresh-keeping film.

[0018] As a preferred scheme of the preparation method of the porous in-situ microfiber active fresh-keeping film of the present invention, among them: the loading of the active substance on the porous skeleton material includes

[0019] Adding the porous skeleton material into a solution containing the active substance, ultrasonicating for 5-10 min, stirring and soaking at a rotation speed of 100-200 rpm for 3-5 h, and drying.

[0020] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the porous skeleton material includes one or more of mesoporous silica, activated carbon, molecular sieve, and zeolite.

[0021] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the mass ratio of the active substance to the porous skeleton material is 1:1 to 2.

[0022] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the active substance includes an ethylene scavenger and / or an antibacterial agent, the ethylene scavenger includes one or more of nano-titanium dioxide, nano-zinc oxide, and potassium permanganate. When the active substance contains both an ethylene scavenger and an antibacterial agent, the mass ratio of the ethylene scavenger to the antibacterial agent is 1:1.

[0023] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the mass ratio of the active substance-porous skeleton material to polymer B is 1 to 5:10.

[0024] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the matrix phase includes one or more of polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer, and the mass ratio of the fiber phase to the matrix phase is 5 to 40:100.

[0025] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the etching of the matrix phase in the in-situ microfibril composite material by the solvent includes

[0026] After wrapping the in-situ microfibril composite material with a copper mesh, it is placed in a good solvent of the matrix phase and etched at the boiling point for 2 to 4 hours. The oriented microfibril phase is randomly arranged under the action of the solvent and piled up to form a porous in-situ microfibril active fresh-keeping film;

[0027] Wherein, the mass ratio of the solvent to the in-situ microfibril composite material is 2:1, and the solvent includes one of xylene, toluene, and chloroform.

[0028] As a preferred embodiment of the preparation method of the porous in-situ microfibril active fresh-keeping film of the present invention, wherein: the process parameters of the micro-nano layer-by-layer co-extrusion are that the processing temperature is 10 to 20 °C above the melting point of the fiber phase, the extrusion speed is 150 to 200 rpm, and the traction speed is 50 to 80 rpm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) In the present invention, the active substance can be slowly and continuously released under the action of the three-dimensional porous network structure and the porous framework material, enabling the ethylene elimination and antibacterial functions of the porous in-situ microfiber active fresh-keeping film to have long-term effectiveness, and effectively preventing the ripening gas ethylene and molds from accelerating the senescence of fruits and vegetables; the three-dimensional porous network structure of the active fresh-keeping film has a modified atmosphere function, and the gas permeability can be regulated by controlling the density of the three-dimensional network structure, so as to maximally inhibit the respiration of fruits and vegetables.

[0031] (2) The in-situ fibrillation technology combined with solvent etching is used to prepare the porous original flavor microfiber active microfiber film. Compared with the electrospinning technology, the preparation process is simple and controllable, and the range of selectable polymers is wider. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0033] Figure 1 It is the morphology diagram of PBAT fibers in the fresh-keeping films prepared in Example 1 and Comparative Example 1 of the present invention.

[0034] Figure 2 It is the comparison diagram of the fresh-keeping effects of bananas exposed to air and wrapped with the fresh-keeping film prepared in Example 1 of the present invention.

[0035] Figure 3 It is the comparison diagram of the fresh-keeping effects of sugarcane wrapped with the fresh-keeping films prepared in Comparative Example 3, Comparative Example 4 and Example 7 of the present invention.

[0036] Figure 4 It is the comparison diagram of the fresh-keeping effects of mangoes exposed to air and wrapped with the fresh-keeping films prepared in Comparative Example 6 and Example 10 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the specific embodiments of the present invention in detail in conjunction with the embodiments of the specification.

[0038] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0039] Second, the "one embodiment" or "embodiment" referred to herein means a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The "in one embodiment" that appears in different places in this specification does not all refer to the same embodiment, nor is it an individual or selectively mutually exclusive embodiment with other embodiments.

[0040] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0041] The method for measuring the microscopic morphology of the porous in-situ microfibril active preservative film of the present invention is as follows: Cut a small piece of the porous in-situ microfibril active preservative film, place it on the surface of the conductive adhesive for gold spraying treatment, and observe the morphology of the fibers under a scanning electron microscope.

[0042] The method for measuring the pore size of the porous in-situ microfibril active preservative film of the present invention is as follows: Use a capillary flow porosimeter to measure the pore size of the porous in-situ microfibril active preservative film. The specific operation is to cut the porous in-situ microfibril active preservative film into a circular sample with a diameter of 4 cm, then soak the circular sample in a beaker containing anhydrous ethanol. After the sample is completely wetted, place it at the bottom of the sample chamber of the instrument, and ensure that the sample can completely cover the O-ring at the bottom of the sample chamber. Then place the upper pressure ring into the sample chamber and press it down, screw on the lid of the sample chamber, connect the air pipe, and turn on the power for testing.

[0043] The method for measuring the gas permeability of the porous in-situ microfibril active preservative film of the present invention is as follows: The carbon dioxide permeation rate and oxygen permeation rate are tested with reference to GB / T 1038-2000 Test method for gas permeability of plastic films and sheets - Differential pressure method; the water vapor transmission rate is tested with reference to GB / T 1037-1988 Test method for water vapor transmission of plastic films and sheets - Cup method.

[0044] The method for testing the ethylene elimination rate of the porous in-situ microfibril active preservative film of the present invention is as follows: After making the film into a sealed fresh-keeping bag, inject 1 ml of ethylene gas into the fresh-keeping bag with a syringe. After 24 hours, use a gas chromatograph to measure the ethylene gas concentration in the fresh-keeping packaging bag. The ethylene elimination rate is calculated by the following formula:

[0045]

[0046] The antibacterial rate of the porous in-situ microfibril active preservative film of the present invention against Escherichia coli and Staphylococcus aureus is tested with reference to GB / T 31402-2015.

[0047] The evaluation method for the freshness preservation performance of the porous in-situ microfiber active fresh-keeping film in the present invention is as follows: Select the same batch of fruits that are complete, undamaged, consistent in hardness and color, and relatively uniform in size. After randomly dividing them equally, seal and preserve them with the prepared film. At room temperature, visually observe every day whether problems such as water loss, shriveling, water leakage, and rotting occur to the fruits. When the fruits start to rot, the freshness preservation period is reached.

[0048] Example 1

[0049] For fruits and vegetables such as bananas that are sensitive to ethylene ripening gas, a porous in-situ microfiber active fresh-keeping film containing an ethylene scavenger is prepared. Specifically:

[0050] (1) Add molecular sieve (porous framework material) to the ethylene scavenger potassium permanganate (active substance) solution, ultrasonicate for 8 min, stir and soak at a speed of 100 rpm for 4 h, and then dry it, so that the ethylene scavenger potassium permanganate is loaded on the molecular sieve to form potassium permanganate - molecular sieve, that is, active substance - porous framework material. Among them, the mass ratio of the active substance (potassium permanganate) to the porous framework material (molecular sieve) is 1:1;

[0051] (2) Melt-blend and pelletize the potassium permanganate - molecular sieve (active substance - porous framework material) prepared in step (1) and PBAT (polymer B) according to a mass ratio of 3:10 to form a fiber phase;

[0052] (3) Mix the fiber phase prepared in step (2) and polyethylene (matrix phase) evenly according to a mass ratio of 25:100, and form an in-situ microfiber composite material through micro-nano layer-by-layer co-extrusion. Among them, the process parameters of micro-nano layer-by-layer co-extrusion are set as follows: the processing temperature is 140 °C, the extrusion speed is 180 rpm, and the traction speed is 60 rpm;

[0053] (4) After wrapping the in-situ microfiber composite material prepared in step (3) with a copper mesh, put it into toluene (a good solvent for the matrix phase), and etch it under boiling conditions for 2 h. The oriented microfiber phase is randomly arranged under the action of the solvent and piled up to form a porous in-situ microfiber active fresh-keeping film. Among them, the mass ratio of toluene to the in-situ microfiber composite material is 2:1.

[0054] Comparative Example 1

[0055] The difference between this comparative example and Example 1 is that no active substance and porous framework material are added, and other steps are the same as those in Example 1, and the fresh-keeping film of this comparative example is prepared.

[0056] Figure 1Morphology diagrams of the fresh-keeping films prepared in Comparative Example 1 and Example 1. Among them, (a) and (a') are PBAT fibers of the inactive substance - skeleton material in Comparative Example 1, and (b) and (b') are PBAT fibers of the active substance - skeleton material in Example 1. It can be seen from the figure that the surface of the PBAT fibers containing the active substance - skeleton material is rough, while the surface of the PBAT fibers without the active substance - skeleton material is smooth.

[0057] The fresh-keeping effect of the fresh-keeping film in Example 1 was tested, and the results are as Figure 2 shown. Among them, (a) is the morphology of the banana without packaging after being stored at room temperature for 8 days, and (b) is the morphology of the banana wrapped with the porous in-situ microfiber active fresh-keeping film prepared in Example 1 after being stored at room temperature for 8 days. Obviously, it can be seen that the fresh-keeping film prepared in Example 1 has a long-term and good fresh-keeping effect on bananas. The main reason is that the ethylene scavenger potassium permanganate in the porous in-situ microfiber active fresh-keeping film is slowly released from the skeleton material, continuously eliminating the ripening effect of ethylene on bananas, thereby prolonging the fresh-keeping period of bananas.

[0058] Example 2

[0059] The difference between this example and Example 1 is that the active substance potassium permanganate is adjusted to nano-zinc oxide, and other steps are the same as those in Example 1, and the fresh-keeping film of this example is prepared.

[0060] Example 3

[0061] The difference between this example and Example 1 is that the mass ratio of the active substance (potassium permanganate) to the porous skeleton material (molecular sieve) is adjusted to 1:1.5, and other steps are the same as those in Example 1, and the fresh-keeping film of this example is prepared.

[0062] Example 4

[0063] The difference between this example and Example 1 is that the mass ratio of potassium permanganate - molecular sieve to PBAT (polymer B) is adjusted to 1:10, and other steps are the same as those in Example 1, and the fresh-keeping film of this example is prepared.

[0064] Example 5

[0065] The difference between this example and Example 1 is that the mass ratio of potassium permanganate - molecular sieve to PBAT (polymer B) is adjusted to 5:10, and other steps are the same as those in Example 1, and the fresh-keeping film of this example is prepared.

[0066] Example 6

[0067] The difference between this example and Example 1 is that the mass ratio of the fiber phase to polyethylene (matrix phase) is adjusted to 5:100, and other steps are the same as those in Example 1, and the fresh-keeping film of this example is prepared.

[0068] The physical properties and preservation effects of the porous in-situ microfiber modified atmosphere preservation films prepared in Examples 1-6 were tested, and the results are shown in Tables 1-2.

[0069] Table 1 Comparison of physical property indexes of porous in-situ microfiber modified atmosphere preservation films

[0070]

[0071] Table 2 Comparison of preservation effects of porous in-situ microfiber modified atmosphere preservation films

[0072]

[0073] According to Tables 1 and 2, for fruits and vegetables such as bananas that are sensitive to ethylene ripening gas, both the porous skeleton loaded with potassium permanganate and the nano-zinc oxide active substance can achieve the preservation effect and play a long-term ethylene elimination role, and the preservation days can reach about 25 days. It can be seen that within the scope of the present invention, long-term preservation of banana-like fruits and vegetables can be achieved. The preservation film prepared under the conditions of Example 1 has a high carbon dioxide and low oxygen permeability, and at the same time a low water vapor permeability, making the bananas in a dormant state and achieving the best effect, and the preservation days can reach 27 days.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that no porous skeleton material is added, and the other steps are the same as those in Example 1, and the preservation film of this comparative example is prepared.

[0076] The physical properties and preservation effects of the preservation films prepared in Comparative Examples 1-2 were tested, and the results are shown in Tables 3-4.

[0077] Table 3 Comparison of physical property indexes of preservation films

[0078]

[0079] Table 4 Comparison of preservation effects of preservation films

[0080]

[0081] According to Tables 3 and 4, when no active substance and porous skeleton material are added, the prepared preservation film has a poor preservation effect on banana-like fruits and vegetables. The effect of the preservation film prepared by only adding the active substance is still poor. This is because the active substance in the preservation film can only be slowly and continuously released under the action of the three-dimensional porous network structure and the porous skeleton material, play a long-term ethylene elimination role, and maximize the extension of the preservation period of fruits and vegetables.

[0082] Example 7

[0083] For perishable fruits and vegetables such as fresh-cut sugarcane that are susceptible to bacterial infection and decay, a porous in-situ microfiber active preservative film containing an antibacterial agent is prepared as follows:

[0084] (1) Mesoporous silica is added to the quercetin solution of the antibacterial agent, ultrasonicated for 5 min, stirred and soaked at a rotation speed of 150 rpm for 3.5 h, and then dried, so that quercetin is loaded on the mesoporous silica to form quercetin-mesoporous silica. Among them, the mass ratio of the active substance to the porous skeleton material is 1:1;

[0085] (2) The quercetin-mesoporous silica prepared in step (1) and PLA are melt-blended and pelletized according to a mass ratio of 2:10 to form a fiber phase;

[0086] (3) The fiber phase prepared in step (2) and the polyolefin elastomer are mixed evenly according to a mass ratio of 30:100, and an in-situ microfiber composite material is formed by micro-nano layer-by-layer coextrusion. Among them, the process parameters of the micro-nano layer-by-layer coextrusion are set as follows: the processing temperature is 190 °C, the extrusion speed is 200 rpm, and the traction speed is 80 rpm;

[0087] (4) After wrapping the in-situ microfiber composite material prepared in step (3) with a copper mesh, it is placed in xylene and etched under boiling conditions for 2 h. The oriented microfiber phase is randomly arranged under the action of the solvent and piled up to form a porous in-situ microfiber active preservative film. Among them, the mass ratio of xylene to the in-situ microfiber composite material is 2:1.

[0088] Example 8

[0089] The difference between this example and Example 7 is that the active substance quercetin is adjusted to cinnamon essential oil, and the other steps are the same as those in Example 7, and the preservative film of this example is prepared.

[0090] Example 9

[0091] The difference between this example and Example 7 is that the mass ratio of the active substance (quercetin) to the porous skeleton material (mesoporous silica) is adjusted to 1:2, and the other steps are the same as those in Example 7, and the preservative film of this example is prepared.

[0092] The physical properties and preservation effects of the porous in-situ microfiber modified atmosphere preservative films prepared in Examples 7 to 9 are tested, and the results are shown in Tables 5 to 6.

[0093] Table 5 Comparison of physical property indexes of porous in-situ microfiber modified atmosphere preservative films

[0094]

[0095] Table 6 Comparison of preservation effects of porous in-situ microfiber modified atmosphere preservative films

[0096]

[0097] As can be seen from Tables 5 to 6, for fresh-cut fruits and vegetables such as fresh-cut sugarcane that are susceptible to bacterial infection and decay, both quercetin and cinnamon essential oil as active substance antibacterial agents can achieve the preservation effect. Within the scope of the present invention, long-term preservation of sugarcane-like fruits and vegetables can be achieved. Under the conditions of Example 1, the prepared fresh-keeping film with high carbon dioxide and low oxygen permeability can effectively inhibit respiration and achieve the best effect, and the preservation days can reach 5 days. When the mass ratio of the active substance (quercetin) to the porous skeleton material (mesoporous silica) is adjusted from 1:1 to 1:2, the preservation effect is slightly lower.

[0098] Comparative Example 3

[0099] This comparative example uses a perforated fresh-keeping bag purchased from Maryya, with a thickness of 0.007 mm, and the main component is polyethylene.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 7 is that no active substance is added, and other steps are the same as those in Example 7, and the fresh-keeping film of this comparative example is prepared.

[0102] The preservation effects of the fresh-keeping films prepared in Comparative Example 3, Comparative Example 4, and Example 7 were tested, and the results are as Figure 3 shown. Among them, (a) is the morphology diagram of sugarcane wrapped with the commercially available fresh-keeping film of Comparative Example 3 after 5 days of preservation at room temperature, (b) is the morphology diagram of sugarcane wrapped with the fresh-keeping film without active substance prepared in Comparative Example 4 after 5 days of preservation at room temperature, and (c) is the morphology diagram of sugarcane wrapped with the porous in-situ microfiber active fresh-keeping film prepared in Example 7 after 5 days of preservation at room temperature. By comparison, it can be seen that the porous in-situ microfiber active fresh-keeping film prepared in Example 7 has the best preservation effect on sugarcane. The main reason is that the quercetin in the mesoporous silica is slowly released, playing a long-term antibacterial role, inhibiting the growth of bacteria on the surface of peeled sugarcane, and prolonging the preservation period of sugarcane.

[0103] Comparative Example 5

[0104] The difference between this example and Example 7 is that the active substance-porous skeleton material is not added, and other steps are the same as those in Example 7, and the fresh-keeping film of this comparative example is prepared.

[0105] The physical properties and preservation effects of the fresh-keeping films prepared in Comparative Examples 3 to 5 were tested, and the results are shown in Tables 7 to 8.

[0106] Table 7 Comparison of physical property indexes of fresh-keeping films

[0107]

[0108]

[0109] Table 8 Comparison of the fresh-keeping effects of fresh-keeping films

[0110]

[0111] As can be seen from the combination of Tables 7 - 8 and Tables 5 - 6, the number of fresh-keeping days of the fresh-keeping film prepared by the invention is more than 3 times that of the commercially available fresh-keeping film for sugarcane-like fruits and vegetables. Without adding antibacterial active substances, the growth of bacteria cannot be inhibited, thus significantly reducing the fresh-keeping duration. Adding porous framework materials can slightly increase the carbon dioxide permeation rate and extend the fresh-keeping days.

[0112] Example 10

[0113] For fruits and vegetables such as mangoes that are sensitive to both ethylene and bacteria, a porous in-situ microfiber active fresh-keeping film containing both an ethylene scavenger and an antibacterial agent is prepared as follows:

[0114] (1) Zeolite is added to a mixed solution of the antibacterial agent thymol and the ethylene scavenger nano-titanium dioxide, ultrasonicated for 10 min, stirred and soaked at a rotation speed of 200 rpm for 5 h, and then dried, so that thymol and nano-titanium dioxide are loaded on the zeolite to form an active substance - porous framework material, wherein the mass ratio of the active substance to the porous framework material is 1:1; the mass ratio of thymol to nano-titanium dioxide is 1:1;

[0115] (2) The active substance - porous framework material prepared in step (1) is melt-blended and pelletized with polypropylene according to a mass ratio of 5:10 to form a fiber phase;

[0116] (3) The fiber phase prepared in step (2) is mixed evenly with ethylene-vinyl acetate copolymer according to a mass ratio of 40:100, and an in-situ microfiber composite material is formed by micro-nano layer-by-layer co-extrusion. Among them, the process parameters of the micro-nano layer-by-layer co-extrusion are set as follows: the processing temperature is 180 °C, the extrusion speed is 160 rpm, and the traction speed is 70 rpm;

[0117] (4) After wrapping the in-situ microfiber composite material prepared in step (3) with a copper mesh, it is placed in chloroform and etched under boiling conditions for 2 h to form a porous in-situ microfiber active fresh-keeping film, wherein the mass ratio of chloroform to the in-situ microfiber composite material is 2:1.

[0118] Example 11

[0119] The difference between this example and Example 10 is that the active substances thymol and nano-titanium dioxide are adjusted to carvacrol and nano-zinc oxide, and the other steps are the same as those in Example 10, and the fresh-keeping film of this example is prepared.

[0120] Example 12

[0121] The difference between this example and Example 10 lies in that the mass ratio of the active substances (the antibacterial agent thymol and the ethylene scavenger nano-titanium dioxide) to the porous framework material (zeolite) is adjusted to 1:2, and the other steps are the same as those in Example 10, and the fresh-keeping film of this example is prepared.

[0122] The physical properties and fresh-keeping effects of the porous in-situ microfibril modified atmosphere fresh-keeping films prepared in Examples 10 to 12 were tested, and the results are shown in Tables 9 to 10.

[0123] Table 9 Comparison of physical property indexes of porous in-situ microfibril modified atmosphere fresh-keeping films

[0124]

[0125] Table 10 Comparison of fresh-keeping effects of porous in-situ microfibril modified atmosphere fresh-keeping films

[0126]

[0127] It can be seen from Tables 9 to 10 that for fruits and vegetables such as mangoes that are sensitive to both ethylene and bacteria, when preparing the fresh-keeping film, the fresh-keeping effect of choosing carvacrol and nano-zinc oxide as the active substances is slightly lower than that of thymol and nano-titanium dioxide. In addition, under the conditions of Example 10, the prepared fresh-keeping film has the highest carbon dioxide transmission rate, the fresh-keeping days can reach 16 days, the highest ethylene elimination rate and antibacterial rate, and the best fresh-keeping effect. When the mass ratio of the active substance to the porous framework material is adjusted from 1:1 to 1:2, the effect is slightly worse.

[0128] Comparative Example 6

[0129] The difference between this example and Example 10 lies in that no active substance is added, and the other steps are the same as those in Example 10, and the fresh-keeping film of this comparative example is prepared.

[0130] The fresh-keeping effects of the fresh-keeping films of Example 10 and Comparative Example 6 were tested, and the results are as Figure 4 shown. Among them, (a) and (a’) are the internal and external morphologies of unpacked mangoes after normal temperature fresh-keeping for 14 days, (b), (b’), and (b”) are the internal and external morphologies of mangoes wrapped with the fresh-keeping film without active substances prepared in Comparative Example 6 after normal temperature fresh-keeping for 14 days, and (c), (c’), and (c”) are the internal and external morphologies of mangoes wrapped with the porous in-situ microfibril active fresh-keeping film prepared in Example 10 after normal temperature fresh-keeping for 14 days. It can be seen that the fresh-keeping film prepared in Example 10 realizes the long-term fresh-keeping of mangoes. The main reasons are that, on the one hand, the transmittance of the porous in-situ microfibril active fresh-keeping film can make mangoes in a low-oxygen and high-carbon dioxide gas atmosphere, inhibiting the respiration; on the other hand, the active substances thymol and nano-titanium dioxide respectively play the roles of long-term antibacterial and ethylene elimination, preventing bacterial growth and the ripening effect of ethylene gas.

[0131] The physical properties and freshness preservation effects of the fresh-keeping film prepared in Comparative Example 6 were tested, and the results are shown in Tables 11-12.

[0132] Table 11 Comparison of physical property indexes of fresh-keeping films

[0133]

[0134] Table 12 Comparison of freshness preservation effects of fresh-keeping films

[0135]

[0136] As can be seen from Tables 11-12, for fruits and vegetables such as mangoes that are sensitive to both ethylene and bacteria, the lack of active substances significantly reduces the freshness preservation effect of the fresh-keeping film.

[0137] In summary, the present invention provides a porous in-situ microfiber active fresh-keeping film and a preparation method thereof. An ethylene scavenger and / or an antibacterial agent is used as an active substance and loaded on a porous skeleton material to obtain an active substance-porous skeleton material. The active substance-porous skeleton material is blended with polymers such as polypropylene and polyamide as the fiber phase, and polyethylene, polyolefin elastomer, etc. are used as the matrix phase. The fiber phase and the matrix phase are mixed and formed into a composite material by micro-nano layer-by-layer co-extrusion. The matrix phase in the composite material is etched with a good solvent to obtain a porous in-situ microfiber active fresh-keeping film.

[0138] Among them, the three-dimensional porous network structure of the active fresh-keeping film has a modified atmosphere function and inhibits the respiration of fruits and vegetables. Under the action of the three-dimensional porous network structure and the porous skeleton material, the active substances in the active fresh-keeping film can be slowly and continuously released, exerting a long-term antibacterial effect and / or ethylene scavenging effect, and maximizing the freshness preservation period of fruits and vegetables.

[0139] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A porous in-situ microfiber active cling film, characterized in that: The porous in-situ microfiber active cling film is a three-dimensional network structure of freely stacked nanofibers, a porous structure is formed between the nanofibers, and the pore size is 10 to 1000 nm; Wherein, the nanofiber is composed of a porous skeleton material and a polymer B, and the porous skeleton material is loaded with an antibacterial agent and / or an ethylene scavenger; The polymer B includes one or more of polylactic acid, polypropylene, polyamide, polyethylene terephthalate, and polybutylene terephthalate adipate; the antibacterial agent includes one or more of quercetin, curcumin, cinnamon essential oil, thymol, and carvacrol.

2. A method for preparing a porous in-situ microfiber active cling film, characterized in that: include, The active substance is loaded on the porous skeleton material to form an active substance-porous skeleton material; The active substance-porous skeleton material and polymer B are melt-blended and pelletized to form a fiber phase; The fiber phase and the matrix phase are uniformly mixed, and an in-situ microfiber composite material is formed by micro-nano lamination co-extrusion; The matrix phase in the in-situ microfiber composite material is etched by a solvent to form a porous in-situ microfiber active cling film.

3. The method for preparing the porous in-situ microfiber active cling film according to claim 2, characterized in that: The active substance is loaded on the porous skeleton material and comprises: The porous skeleton material is added into the solution containing the active substance, ultrasonicated for 5 to 10 minutes, stirred and immersed at a speed of 100 to 200 rpm for 3 to 5 hours, and dried.

4. The method for preparing the porous in-situ microfiber active cling film according to claim 3, characterized in that: The porous framework material includes one or more of mesoporous silica, activated carbon, molecular sieve, and zeolite.

5. The method for preparing the porous in-situ microfiber active cling film according to claim 3, characterized in that: The mass ratio of the active substance to the porous skeleton material is 1:1-2.

6. The method for preparing the porous in-situ microfiber active cling film according to claim 3, characterized in that: The active substance includes an ethylene scavenger and / or an antibacterial agent; when the active substance contains both an ethylene scavenger and an antibacterial agent, the mass ratio of the ethylene scavenger to the antibacterial agent is 1:1; the ethylene scavenger includes one or more of nano titanium dioxide, nano zinc oxide, and potassium permanganate.

7. The method for preparing the porous in-situ microfiber active cling film according to claim 2, characterized in that: The mass ratio of the active substance-porous skeleton material to polymer B is 1 to 5:

10.

8. The method for preparing the porous in-situ microfiber active cling film according to claim 2, characterized in that: The matrix phase includes one or more of polyethylene, polyolefin elastomer, and ethylene-vinyl acetate copolymer, and the mass ratio of the fiber phase to the matrix phase is 5 to 40:

100.

9. The method for preparing the porous in-situ microfiber active cling film according to claim 2, characterized in that: The process parameters of the micro-nano stacking co-extrusion are: the processing temperature is 10-20° C. above the melting point of the fiber phase, the extrusion speed is 150-200 rpm, and the pulling speed is 50-80 rpm.

10. The method for preparing the porous in-situ microfiber active cling film according to claim 2, characterized in that: The etching of the matrix phase in the in-situ microfiber composite material by a solvent comprises: After wrapping the in-situ microfiber composite with a copper mesh, the composite was placed in a good solvent of the matrix phase and etched under boiling conditions for 2 ～ 4h, the oriented microfibrils are randomly arranged under the action of the solvent and stacked to form a porous in-situ microfibril active cling film; Wherein, the solvent includes one of xylene, toluene and chloroform.

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