One-way condensate discharge composite layer and modified atmosphere preservation bag

Abstract

The application belongs to the technical field of modified atmosphere packaging, and discloses a one-way condensate discharge composite layer and a modified atmosphere preservation bag. The composite layer comprises a hydrophilic porous layer and a hydrophobic nuclear pore membrane layer. The hydrophilic porous layer is located on the first side of the composite layer, and the hydrophobic nuclear pore membrane layer is located on the second side of the composite layer. The hydrophobic nuclear pore membrane layer is a polymer nuclear pore membrane formed by heavy ion irradiation etching, is provided with a plurality of tapered channels, and at least the surface facing the second side is hydrophobically modified. The composite layer is configured to allow water vapor after condensate vaporization to penetrate from the first side to the second side, and to block external liquid water from penetrating from the second side to the first side. The modified atmosphere preservation bag comprises a bag body and the composite layer. The inner and outer surfaces of the bag body are provided with a hydrophobic coating. A window is formed on the bag body, and the composite layer is sealingly connected to the window. The application can direct the discharge of liquid condensate formed by condensation in the bag, and reduce the accumulation of free liquid water.

Description

Technical Field

[0001] This invention relates to the field of modified atmosphere packaging technology, and in particular to a one-way decondensation-removing composite layer and a modified atmosphere bag. Background Technology

[0002] Fresh fruits and vegetables are still living tissues after harvesting, continuously releasing water vapor through transpiration. When these fruits and vegetables are placed in a preservation bag, the relatively enclosed space allows the water vapor released through transpiration to gradually accumulate inside, naturally creating a high relative humidity environment. However, under high humidity conditions, when the bag wall temperature is below the dew point temperature, the water vapor inside the bag easily condenses into liquid water droplets. Existing ordinary preservation bags typically lack the ability to conduct condensation, allowing water droplets to easily adhere to the bag wall and drip onto the surface of the fruits and vegetables, providing conditions for mold and bacteria growth and accelerating spoilage. While some existing microporous breathable preservation bags can achieve a certain degree of gas exchange, they cannot actively remove condensed liquid water droplets, and free liquid water easily accumulates inside the bag. Furthermore, existing core-pore membrane preservation bags primarily focus on gas exchange and lack structures for collecting, conducting, and draining liquid condensation, making it difficult to directionally drain the liquid condensation that has formed inside the bag. Summary of the Invention

[0003] To address the shortcomings of the prior art, this invention provides a one-way condensation-removing composite layer and a modified atmosphere packaging bag containing the composite layer. Through the composite structure of a hydrophilic porous layer and a hydrophobic core-porous membrane layer, the liquid condensation formed inside the bag is captured, conducted, and vaporized and discharged, while simultaneously preventing external liquid water and microorganisms from entering in reverse, thereby reducing the impact of free liquid water inside the bag on fruits and vegetables.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A unidirectional condensation-dissipating composite layer includes a hydrophilic porous layer and a hydrophobic core-pore membrane layer; the hydrophilic porous layer is composite with the hydrophobic core-pore membrane layer, the hydrophilic porous layer is located on a first side of the composite layer, and the hydrophobic core-pore membrane layer is located on a second side of the composite layer; the hydrophobic core-pore membrane layer is a polymer core-pore membrane formed by heavy ion irradiation etching, and has multiple conical channels, and at least the surface of the hydrophobic core-pore membrane layer facing the second side is hydrophobically modified; the composite layer is configured to allow water vapor after condensation vaporization to permeate from the first side to the second side, and to block external liquid water from permeating from the second side to the first side.

[0005] Furthermore, the substrate of the hydrophobic core-pore membrane layer is a PET membrane or a PC membrane, with a membrane thickness of 3-10 μm.

[0006] Optionally, the thickness of the hydrophobic core-pore membrane layer can also be 3-30 μm.

[0007] Furthermore, the small-end diameter of the tapered channel is 0.1-3 μm.

[0008] Furthermore, the irradiation conditions for the hydrophobic core-pore membrane are: ion energy 0.3-1 MeV / u, irradiation flux 1×10⁻⁶. 7 -1×10 9 / cm 2 Ions completely penetrate the polymer film to form columnar latent tracks; the etching conditions are: the etching solution is a 2-6 mol / L NaOH solution, the solvent is a mixed solution of methanol and water, the methanol content is 10%-80%, the etching temperature is 50℃-80℃, and the etching time is 5-15 minutes.

[0009] Alternatively, the ion energy can be 0.3-50 MeV / u, and the irradiation flux can be 1×10⁻⁶. 6 -1×10 9 / cm 2 .

[0010] Furthermore, the hydrophobic modification is a silicone hydrophobic coating deposited by PECVD, with the following deposition conditions: silicone monomer as precursor, argon as carrier gas, RF power not exceeding 90 W, cavity pressure 15-25 Pa, substrate temperature not exceeding 50℃, and deposition time 120-600 s.

[0011] Furthermore, the hydrophilic porous layer is a hydrophilic nonwoven fabric and is loaded with antibacterial materials.

[0012] Furthermore, the antibacterial material is a silver ion antibacterial agent or a plant-derived antibacterial agent.

[0013] The present invention also provides a modified atmosphere packaging bag, comprising a bag body and the aforementioned composite layer. Both the inner and outer surfaces of the bag body are coated with a hydrophobic coating. A window is provided on the bag body, and the composite layer is sealed to the window, with the first side facing inwards and the second side facing outwards.

[0014] Furthermore, the area of ​​the window accounts for 2%-12% of the total area of ​​the bag; the bag substrate is PE film or PP modified film.

[0015] Furthermore, the composite layer is heat-sealed or adhesively sealed to the window.

[0016] The beneficial effects of this invention are as follows: The composite structure of a hydrophilic porous layer and a hydrophobic core-porous membrane layer captures liquid water droplets condensing inside the bag and conducts them to the interface of the hydrophobic core-porous membrane layer. The liquid water vaporizes at the interface and is discharged outwards as water vapor through the core-porous membrane. Simultaneously, the hydrophobic core-porous membrane layer prevents external liquid water and microorganisms from entering. Therefore, the liquid condensation already formed inside the bag can be directionally discharged, reducing the risk of free liquid water droplets accumulating inside the bag and dripping onto the surface of fruits and vegetables, thus helping to reduce the probability of spoilage. Attached Figure Description

[0017] Figure 1 This is a side cross-sectional view of the composite layer in one embodiment of the present invention.

[0018] Figure 2 This is a rear view of a modified atmosphere packaging bag with the composite layer assembled, according to an embodiment of the present invention.

[0019] In the diagram: 100, composite layer; 101, first side; 102, second side; 110, hydrophilic porous layer; 120, hydrophobic core-pore membrane layer; 121, conical channel; 200, modified atmosphere packaging bag; 210, bag body. Detailed Implementation

[0020] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0021] In the description of this invention, it should be noted that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In the description of this invention, it should be noted that the terms "first side" and "second side" are used only to distinguish the two sides of the composite layer to facilitate the description of the positional relationship between the hydrophilic porous layer and the hydrophobic core-pore membrane layer, and should not be construed as an absolute limitation on the orientation of the composite layer. Similarly, directional terms such as "inner side" and "outer side" refer to modified atmosphere packaging bags, with the side facing the bag cavity as the inner side and the side away from the bag cavity as the outer side.

[0024] The preferred embodiments of this application will be further described below with reference to the accompanying drawings.

[0025] likeFigure 1 As shown, the present invention provides a unidirectional condensation-removing composite layer 100, comprising a hydrophilic porous layer 110 and a hydrophobic core-pore membrane layer 120; the hydrophilic porous layer 110 and the hydrophobic core-pore membrane layer 120 are composite, the hydrophilic porous layer 110 is located on the first side 101 of the composite layer 100, and the hydrophobic core-pore membrane layer 120 is located on the second side 102 of the composite layer 100; the hydrophobic core-pore membrane layer 120 is a polymer core-pore membrane formed by heavy ion irradiation etching, and has a plurality of conical channels 121, and the surface of the hydrophobic core-pore membrane layer 120 at least facing the second side 102 is hydrophobically modified; the composite layer 100 is configured to allow water vapor after condensation to permeate from the first side 101 to the second side 102, and to block external liquid water from permeating from the second side 102 to the first side 101.

[0026] Specifically, the composite layer 100 is a two-layer composite structure, with the first side 101 facing inwards when in use and the second side 102 facing outwards when in use. A hydrophilic porous layer 110 is disposed on the first side 101, and a hydrophobic core-pore membrane layer 120 is disposed on the second side 102.

[0027] Furthermore, the substrate of the hydrophobic core-porous membrane layer 120 is a PET membrane or a PC membrane, with a thickness of 3-30 μm, preferably 3-10 μm. Within the preferred range of 3-10 μm, the core-porous membrane can balance mechanical strength and water vapor permeation efficiency. In the extended range of 10-30 μm, the core-porous membrane can still form interconnected conical channels, but the path of water vapor through the channels becomes longer, requiring higher ion energy and irradiation flux, thus increasing preparation costs and equipment requirements. Those skilled in the art can select a suitable membrane thickness within the 3-30 μm range based on the type of fruit and vegetable, packaging environment, and water production rate.

[0028] The conical pore 121 is arranged along the thickness direction of the hydrophobic core-pore membrane layer 120, with the smaller end of the conical pore 121 facing the second side 102 and the larger end facing the first side 101. The pore diameter of the smaller end of the conical pore 121 is 0.1-3 μm. Within this range, the pore diameter allows water vapor molecules to pass through smoothly while effectively blocking liquid water and common microorganisms.

[0029] It is understood that the diameter of the larger end of the tapered channel 121 is larger than the diameter of the smaller end, and the ratio of the larger end diameter to the smaller end diameter can be 1.5:1 to 5:1, but is not limited to this. A larger larger end diameter facilitates the rapid entry of water vapor into the channel; a smaller end diameter helps improve the blocking accuracy. It should be noted that, unless otherwise specified, the diameter of the tapered channel described in this invention refers to the diameter of the smaller end.

[0030] It should be noted that the composite layer 100 is configured to allow water vapor after condensation to permeate from the first side 101 to the second side 102, while blocking external liquid water from permeating from the second side 102 to the first side 101. This functionality is achieved structurally by the hydrophilic porous layer 110, the hydrophobic core pore membrane layer 120, the conical channel 121, and the hydrophobic modification of the surface of the hydrophobic core pore membrane layer 120.

[0031] Specifically, the hydrophilic porous layer 110 possesses both hydrophilicity and a porous structure, enabling it to capture liquid water droplets condensed within the bag and spread and conduct the liquid water to the inner interface of the hydrophobic core-porous membrane layer 120 via capillary action. The liquid water vaporizes into water vapor at the inner interface of the hydrophobic core-porous membrane layer 120. Since the diameter of water vapor molecules is much smaller than the small-aperture diameter of the conical channel 121, it can easily diffuse and exit through the conical channel 121 to the second side 102. Furthermore, the hydrophobic modification of the surface of the hydrophobic core-porous membrane layer 120 makes it difficult for external liquid water to wet its surface. Under the action of surface tension, external liquid water cannot enter the conical channel 121, thus achieving unidirectional permeability.

[0032] Furthermore, regarding the barrier against external microorganisms, it should be noted that this is the result of the combined effects of pore size selection, hydrophobic modification, conical pore orientation, and antibacterial materials. Specifically, the pore size at the small end of the conical pore 121 is 0.1-3 μm. Most common microorganisms are larger than the lower limit of this pore size range, making it difficult for them to enter the bag through the pores. The hydrophobic modification of the surface of the hydrophobic core-porous membrane layer 120 makes it difficult for external liquid water to wet the inner wall of the pores, and the lack of liquid water carriers for microorganisms further reduces the possibility of entry. The small end of the conical pore 121 faces the second side 102, increasing the difficulty for microorganisms to enter from the outside. The antibacterial material loaded on the hydrophilic porous layer 110 can inhibit the entry of a small number of microorganisms.

[0033] Furthermore, the preparation process of the hydrophobic core-pore membrane layer 120 is as follows: S1. Heavy ion irradiation: The polymer film is irradiated with heavy ions provided by a high-energy accelerator, with an ion energy of 0.3-50 MeV / u, preferably 0.3-1 MeV / u; the irradiation flux is 1×10⁻⁶. 6 -1×10 9 / cm 2 Preferably 1×10 7 -1×10 9 / cm 2 Ions completely penetrate the polymer film to form columnar latent tracks.

[0034] S2. Composite with hydrophilic porous layer: The irradiated polymer film is hot-pressed with the hydrophilic porous layer 110 to form a support for the polymer film.

[0035] S3. Etching: The composite film is placed in an etching solution for etching. The etching solution is a 2-6 mol / L NaOH solution, the solvent is a mixed solution of methanol and water, the methanol content is 10%-80%, the etching temperature is 50℃-80℃, and the etching time is 5-15 minutes. The etching solution contacts the polymer film through the pores of the hydrophilic porous layer 110 and etches along the columnar under-track to form conical channels 121.

[0036] In S1, the ion energy and irradiation flux are within the preferred range described above, which is beneficial for forming columnar latent tracks with uniform pore size on the polymer film. Within the extended range, as the film thickness increases, the required ion energy and irradiation flux correspondingly increase to ensure complete ion penetration of the film. Those skilled in the art can adjust the ion energy and irradiation flux according to the film thickness and pore size requirements, within the range of 0.3-50 MeV / u and 1×10⁻⁶. 6 -1×10 9 / cm 2 Choose the appropriate parameters within the specified range.

[0037] This invention employs a sequence of irradiation, lamination, and etching, utilizing a hydrophilic porous layer 110 as a support layer, which is beneficial for improving the yield of the preparation process. Especially for thin core-pore membranes, such as those with a thickness in the range of 3-10 μm, if pores are etched first and then laminated with the hydrophilic porous layer, the etched film is prone to damage during the lamination process. Adopting a lamination-then-etching sequence effectively improves the yield. Furthermore, since hot-pressing lamination is performed before etching, the hot-pressing temperature needs to be controlled within a low range to avoid adversely affecting the latent track structure in the polymer film. Optionally, the hot-pressing temperature in S2 is less than 60°C, and the hot-pressing pressure can be selected according to the material and thickness of the polymer film, aiming to achieve bonding of the two layers without affecting subsequent etching.

[0038] It should be noted that nuclear pore membranes prepared by conventional heavy ion irradiation etching typically have cylindrical, straight-through pores. The conical pores 121 described in this invention can be formed through a single-sided etching process, where only one side of the polymer film contacts the etching solution during etching, while the other side is shielded by a protective layer, thus forming conical pores with a gradually changing pore size along the film thickness direction. The protective layer can be a material capable of blocking the etching solution, such as alkali-resistant tape or polytetrafluoroethylene film, but is not limited to these. The protective layer can be applied to one side of the polymer film by adhesive bonding or coating. Optionally, surfactant-controlled etching or step-by-step etching can also be used to create a conical structure in the pores. Through these methods, the smaller end of the conical pore 121 faces the second side 102, and the larger end faces the first side 101, which helps to improve the barrier effect against liquid water and microorganisms while allowing water vapor to pass through.

[0039] Under the aforementioned irradiation and etching conditions, uniformly sized, interconnected conical channels can be formed on the polymer film. Specifically, since the thickness of the nuclear pore membrane in this invention is preferably 3-10 μm, compared to conventional thicker nuclear pore membranes, the required ion energy and irradiation flux can be correspondingly reduced, and the etching time can also be shortened. This benefits both by reducing manufacturing costs and the requirements for high-energy accelerators and other equipment, and by improving production efficiency, making this type of nuclear pore membrane more suitable for large-scale production and commercial application. It is understood that, provided that interconnected channels can be formed, the irradiation ion energy, irradiation flux, etching solution concentration, methanol content, etching temperature, and etching time can all be adjusted within a reasonable range.

[0040] The hydrophobic modification refers to the deposition of an organosilicon hydrophobic coating using plasma-enhanced chemical vapor deposition (PECVD). PECVD involves introducing a precursor gas into a low-pressure chamber, activating the precursor gas with radio frequency plasma, causing it to chemically react on the surface and walls of the core pore membrane and deposit to form a hydrophobic coating. The PECVD deposition conditions are: organosilicon monomer as the precursor, argon as the carrier gas, radio frequency power not exceeding 90 W, chamber pressure 15-25 Pa, substrate temperature not exceeding 50°C, and deposition time 120-600 s. Specifically, the organosilicon monomer can be hexamethyldisiloxane or heptamethyldisiloxane, but is not limited to these. Depositing an organosilicon hydrophobic coating on the surface and walls of the core pore membrane using PECVD can impart hydrophobicity to the surface and inner walls of the pores without clogging the micropores, thus improving the water-blocking effect.

[0041] Furthermore, before depositing the hydrophobic coating, the nuclear pore membrane can be subjected to plasma activation treatment, for example, by introducing argon gas and treating it for 60-180 s under the conditions of Ar flow rate 25-35 sccm, cavity pressure 10-20 Pa, and radio frequency power 60-90 W, in order to introduce active sites and improve the adhesion between the hydrophobic coating and the surface of the nuclear pore membrane.

[0042] It should be noted that the above-described PECVD deposition conditions are a preferred embodiment of the present invention. Those skilled in the art will understand that, without clogging the micropores, the RF power, cavity pressure, substrate temperature, and deposition time can all be adjusted within a reasonable range. Furthermore, hydrophobic modification can also be achieved through other methods, including but not limited to conventional hydrophobication treatments such as dip coating, spraying, and grafting, as long as a hydrophobic layer can be formed on the surface of the core pore membrane and the inner wall of the pores.

[0043] In a preferred embodiment, the hydrophilic porous layer 110 is a hydrophilic nonwoven fabric loaded with an antibacterial material. The antibacterial material is a silver ion antibacterial agent or a plant-derived antibacterial agent. The hydrophilic nonwoven fabric has a rich porous structure and good hydrophilicity, enabling it to quickly capture liquid water and conduct it to the interface of the hydrophobic core-porous membrane layer 120. The antibacterial material loaded on the hydrophilic nonwoven fabric can inhibit the growth of microorganisms that may exist in the captured liquid water, reducing the risk of the nonwoven fabric becoming a carrier for microbial growth.

[0044] Furthermore, the antibacterial material can be loaded onto the fiber surface of a hydrophilic nonwoven fabric. The type of antibacterial material can be selected according to actual needs.

[0045] Because this invention employs a process sequence of first lamination and then etching, the etching solution needs to contact the polymer film through the pores of the hydrophilic porous layer 110. Therefore, the hydrophilic nonwoven fabric also needs to possess alkali resistance and temperature resistance to withstand 2-6 mol / L NaOH solution and etching temperatures of 50℃-80℃. Optionally, the hydrophilic nonwoven fabric can be a hydrophilically modified polyester nonwoven fabric. Polyester (PET) nonwoven fabric has good alkali resistance and temperature resistance, making it suitable for the etching process of this invention. The hydrophilic porous layer 110 can also be made of other materials with hydrophilic and porous structures, including but not limited to hydrophilic porous membranes and hydrophilic fiber felts.

[0046] It is understood that the main function of the hydrophilic porous layer 110 is to capture liquid water and conduct it to the interface of the hydrophobic core-pore membrane layer 120. Therefore, any hydrophilic porous material that can achieve this function and can withstand the etching process conditions can be used in this invention.

[0047] like Figure 2 As shown, the present invention also provides a modified atmosphere packaging bag 200, including a bag body 210 and the aforementioned composite layer 100. Both the inner and outer surfaces of the bag body 210 are provided with a hydrophobic coating. A window is provided on the bag body 210, and the composite layer 100 is sealed to the window, with the first side 101 facing inwards and the second side 102 facing outwards.

[0048] Optionally, such as Figure 2 As shown, the window can be located in the middle of the back of the bag body 210, so that condensation droplets inside the bag can roll down the bag wall and collect at the window. Furthermore, the bag body 210 can also be provided with a sealing structure. The sealing structure can be a heat seal, a self-sealing strip, or a tie, but is not limited to these. The sealing structure is used to close the bag body after the fruits and vegetables are filled, creating a relatively closed storage environment inside the bag.

[0049] Both the inner and outer surfaces of the bag body 210 are coated with a hydrophobic coating, preventing condensation droplets on the inner wall of the bag from adhering and causing them to roll down the bag wall under gravity, eventually collecting at the location of the composite layer 100. It should be noted that the hydrophobic treatment methods for the bag body 210 include, but are not limited to, spraying a hydrophobic coating, dipping a hydrophobic coating, plasma surface treatment, chemical grafting modification, blending modification, or surface micro / nano structure construction. Optionally, the hydrophobic coating can be made of hydrophobic materials such as fluorosilanes or siloxanes. The substrate of the bag body 210 can be a PE film or a modified PP film, or other film materials suitable for fruit and vegetable preservation packaging.

[0050] Furthermore, the area of ​​the window occupies 2%-12% of the total area of ​​the bag body 210. Within this range, it is beneficial to balance the condensation discharge rate and the natural maintenance of humidity inside the bag. If the window area is too small, the condensation discharge rate may not be sufficient to match the water production rate of fruit and vegetable transpiration; if the window area is too large, excessive water vapor may be lost from inside the bag.

[0051] Optionally, the composite layer 100 is sealed to the window by heat sealing or adhesive bonding. The sealing connection method between the composite layer 100 and the bag body 210 can be selected according to the bag body material and the composite layer material, including but not limited to heat sealing, adhesive bonding, ultrasonic welding, etc. It should be noted that the sealing connection here is the assembly connection between the composite layer 100 and the bag body 210, which is a different process step from the internal heat-pressing bonding of the composite layer 100.

[0052] It should be noted that in this invention, the first side 101 of the composite layer 100 faces inwards towards the bag, and the second side 102 faces outwards towards the bag. Liquid water droplets condensing inside the bag roll down the hydrophobic bag wall to the composite layer 100, where they are captured by the hydrophilic porous layer 110 and conducted to the interface of the hydrophobic core-pore membrane layer 120. The liquid water vaporizes at the interface and is discharged outwards through the conical pores 121 as water vapor. Because the hydrophobic core-pore membrane layer 120 is hydrophobically modified, external liquid water and microorganisms cannot penetrate the core-pore membrane and enter the bag in the opposite direction. Thus, liquid condensation is discharged unidirectionally from inside the bag to the outside, reducing the accumulation of free liquid water inside the bag. Optionally, the window area of ​​the composite layer 100 can be selected according to the type of fruit and vegetable and the packaging environment to adjust the condensation discharge rate and maintain the humidity inside the bag within a suitable range for fruit and vegetable preservation.

[0053] To facilitate understanding of the technical effects of this invention, several specific application examples are provided below.

[0054] In the first application example, the modified atmosphere packaging bag can be used for packaging leafy vegetables. Leafy vegetables have a high respiration rate and strong transpiration, resulting in high humidity inside the bag after being placed in it. Condensation droplets easily adhere to the walls of ordinary packaging bags, and these droplets, when dripping onto the surface of the leaves, can accelerate spoilage. The modified atmosphere packaging bag of this invention uses a hydrophobic bag wall to allow condensation droplets to roll down the bag wall to the composite layer, where they are captured by the hydrophilic porous layer and conducted to the hydrophobic core-pore membrane interface. After vaporization, the droplets are discharged outside the bag, reducing contact between free liquid water and the leaves, thus helping to lower the probability of spoilage. Optionally, because leafy vegetables have a high respiration rate and rapid water production, the window area can be set relatively large, for example, accounting for about 8% of the total bag area, to match their high water production rate; the pore size at the small end of the core-pore membrane can be about 0.8 μm, balancing water vapor permeability and microbial barrier. Optionally, the leafy vegetables include, but are not limited to, spinach, lettuce, bok choy, and romaine lettuce.

[0055] In the second application example, the modified atmosphere packaging bag can be used for packaging berries. Berries have a moderate respiration rate but thin skins. Condensation droplets formed inside ordinary packaging bags can easily cause the fruit to rot when they drip onto the surface. Because berries have thin skins and are prone to rotting when wet, the window area can be set relatively small, for example, about 3% of the total bag area, to reduce contact between the fruit and the window area. Simultaneously, to ensure the water vapor can escape through the small window, the pore size at the small end of the core pore membrane can be appropriately increased, for example, to about 1.5 μm. The hydrophilic porous layer can be loaded with plant-derived antibacterial agents to further inhibit microbial growth. Thus, while draining condensate, the risk of the fruit rotting due to water contact is reduced. Optionally, the berries include, but are not limited to, strawberries, blueberries, raspberries, and grapes.

[0056] In the third application example, the modified atmosphere packaging bag can be used for fruit and vegetable preservation packaging in cold chain transportation environments. During cold chain transportation, fluctuations in ambient temperature may cause water vapor condensation inside the bag. Ordinary preservation bags do not have the ability to conduct condensation, and condensate easily accumulates inside the bag. The hydrophobic bag wall and composite layer structure of the modified atmosphere packaging bag can direct the condensate droplets out under temperature fluctuation conditions, reducing the accumulation of free liquid water inside the bag. Optionally, the window area can be selected according to the respiration intensity of the fruits and vegetables and the ambient temperature of the transportation environment, for example, accounting for about 5% of the total area of ​​the bag; the pore size of the small end of the core-pore membrane can be about 1.0 μm. Optionally, the cold chain transportation environment includes, but is not limited to, refrigerated truck transportation, cold storage, and cold chain distribution.

[0057] In the fourth application example, the modified atmosphere packaging bag can be used for the preservation and packaging of edible fungi. Edible fungi have a high respiration rate, easily forming a high-humidity environment and producing condensation inside the bag during storage. In ordinary preservation bags, condensation dripping onto the surface of the fungi can easily cause them to soften, become sticky, or even rot. The hydrophobic bag wall and composite layer structure of the modified atmosphere packaging bag can direct the condensation droplets out, reducing contact between condensation and the surface of the edible fungi. Optionally, due to the high respiration rate and rapid water production rate of edible fungi, the window area can be set relatively large, for example, occupying about 8% of the total bag area, to match its water production rate; the pore size at the small end of the nucleopore membrane can be about 1.0 μm. Optionally, the edible fungi include, but are not limited to, shiitake mushrooms, oyster mushrooms, enoki mushrooms, and king oyster mushrooms.

[0058] In the fifth application example, the modified atmosphere packaging bag can be used for packaging fresh-cut fruits and vegetables. Fresh-cut fruits and vegetables have exposed cut surfaces, resulting in high respiration rates and increased surface moisture, making them more susceptible to microbial growth. In ordinary food storage bags, condensation from the cut surfaces can accelerate microbial proliferation. The composite layer of the modified atmosphere packaging bag directs the condensation outwards, while the antibacterial material loaded on the hydrophilic porous layer inhibits microorganisms in the captured liquid water. Optionally, because fresh-cut fruits and vegetables have high water production rates and are easily contaminated, the window area can be relatively large, for example, occupying about 10% of the total bag area, to facilitate timely condensation drainage; the pore size at the small end of the nucleopore membrane can be about 0.5 μm to improve the barrier effect against microorganisms. Optionally, the fresh-cut fruits and vegetables include, but are not limited to, fresh-cut broccoli, fresh-cut carrots, and fresh-cut apples.

[0059] In the sixth application example, the modified atmosphere packaging bag can be used for preserving flowers or cut flowers. Flowers also release moisture during transportation and storage, and condensation formed inside ordinary preservation bags can cause petals to rot. The hydrophobic bag wall and composite layer structure of the modified atmosphere packaging bag can direct condensation droplets out, reducing contact between condensation and the petals. Optionally, the window area can be set relatively moderately, for example, occupying about 4% of the total bag area; the pore size at the small end of the nucleopore membrane can be about 1.5 μm. Optionally, the flowers include, but are not limited to, cut flowers such as roses, carnations, and lilies.

[0060] In the seventh application example, the modified atmosphere packaging bag can be used for small retail packages of fruits and vegetables. Retail packages typically have a small capacity per bag, resulting in a relatively concentrated accumulation of condensation inside. Ordinary food storage bags are more prone to condensation buildup in such a small space. The composite layer of the modified atmosphere packaging bag can be located in the center of the back of the bag, and the window area can be adjusted proportionally according to the bag size, for example, occupying approximately 5% of the total bag area; the pore size of the core-pore membrane can be approximately 0.8 μm. Optionally, the retail packages can be used for repackaging fruits and vegetables in supermarkets, convenience stores, or online fresh food retailers.

[0061] In some extended embodiments, the thickness of the hydrophobic core-pore membrane can be selected in the range of 3-30 μm, the ion energy of the heavy ion irradiation can be selected in the range of 0.3-50 MeV / u, and the irradiation flux can be 1×10⁻⁶. 6 -1×10 9 / cm 2 The selection is within a certain range. For example, for nuclear pore membranes with thicker film and larger pore size, a higher ion energy and irradiation flux can be selected to ensure that ions completely penetrate the film and form a continuous columnar latent track; for nuclear pore membranes with thinner film and smaller pore size, a lower ion energy and irradiation flux can be selected to reduce preparation costs and equipment requirements. Therefore, the composite layer of the present invention can adapt to the different requirements of fruit and vegetable packaging for nuclear pore membrane parameters.

[0062] Optionally, the modified atmosphere packaging bag can also be used in other packaging scenarios requiring condensation control, including but not limited to packaging for preserving traditional Chinese medicine and moisture-proof packaging for tea. It is understood that the above application examples are only used to illustrate the technical effects of the present invention and do not constitute a limitation on the scope of application of the present invention.

[0063] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Furthermore, the window area and aperture in the above application examples are merely illustrative, and those skilled in the art can adjust them according to the type of fruit and vegetable, packaging environment, and water production rate. Various modifications and variations of the present invention are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0064] Optionally, in one embodiment, the edge of the hydrophilic porous layer 110 may extend beyond the edge of the hydrophobic core-porous membrane layer 120. Thus, the exposed edge of the hydrophilic porous layer 110 can directly contact liquid water droplets rolling down the bag wall, increasing the liquid water capture area. Optionally, the hydrophilic porous layer 110 and the hydrophobic core-porous membrane layer 120 may have the same dimensions to facilitate roll-to-roll composite processing.

[0065] Optionally, the modified atmosphere packaging bag 200 may have one or more windows. When there are multiple windows, they may be spaced apart along the width of the bag body 210 to increase the condensation collection area. Optionally, the shape of the window may be rectangular, circular, elongated, etc., but is not limited to these.

[0066] Optionally, the modified atmosphere packaging bag 200 can be manufactured using a roll-to-roll continuous production process. Specifically, a composite layer 100 can be formed by hot-pressing a hydrophilic porous layer 110 and a hydrophobic core-porous membrane layer 120. Then, a window is made on the bag body 210, and the composite layer 100 is sealed to the window to obtain the modified atmosphere packaging bag 200. Using a roll-to-roll continuous production process improves production efficiency, reduces manufacturing costs, and is suitable for large-scale production.

[0067] It is understood that the technical features in the above embodiments can be combined with each other without conflict. The specific values, materials, and process conditions described in this specification are merely illustrative and can be adjusted by those skilled in the art according to actual needs.

[0068] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A unidirectional condensation-removing composite layer, characterized in that: It includes a hydrophilic porous layer and a hydrophobic core-pore membrane layer; The hydrophilic porous layer is combined with the hydrophobic core-pore membrane layer, wherein the hydrophilic porous layer is located on the first side of the composite layer and the hydrophobic core-pore membrane layer is located on the second side of the composite layer; The hydrophobic core pore membrane is a polymer core pore membrane formed by heavy ion irradiation etching, and has multiple conical channels. The surface of the hydrophobic core pore membrane facing at least the second side is hydrophobically modified. The composite layer is configured to allow water vapor from condensation to permeate from the first side to the second side, while blocking external liquid water from permeating from the second side to the first side.

2. The unidirectional condensation-removing composite layer according to claim 1, characterized in that: The substrate of the hydrophobic core-pore membrane is a PET membrane or a PC membrane, with a membrane thickness of 3-10 μm.

3. The unidirectional condensation-removing composite layer according to claim 1, characterized in that: The small end diameter of the tapered channel is 0.1-3 μm.

4. The unidirectional condensation-removing composite layer according to claim 1, characterized in that: The irradiation conditions for the hydrophobic core-pore membrane are: ion energy 0.3-1 MeV / u, irradiation flux 1×10⁻⁶. 7 -1×10 9 / cm 2 Ions completely penetrate the polymer film, forming columnar latent tracks; The etching conditions are as follows: the etching solution is a 2-6 mol / L NaOH solution, the solvent is a mixed solution of methanol and water with a methanol content of 10%-80%, the etching temperature is 50℃-80℃, and the etching time is 5-15 minutes.

5. The unidirectional condensation-removing composite layer according to claim 1, characterized in that: The hydrophobic modification is a silicone hydrophobic coating deposited by PECVD. The deposition conditions are as follows: using silicone monomer as precursor and argon as carrier gas, the deposition is carried out for 120-600s under the conditions of radio frequency power not exceeding 90 W, cavity pressure 15-25 Pa and substrate temperature not exceeding 50℃.

6. The unidirectional condensation-removing composite layer according to claim 1, characterized in that: The hydrophilic porous layer is a hydrophilic nonwoven fabric loaded with antibacterial materials.

7. The unidirectional condensation-removing composite layer according to claim 6, characterized in that: The antibacterial material is a silver ion antibacterial agent or a plant-derived antibacterial agent.

8. A modified atmosphere packaging bag, characterized in that, Includes a bag body and a composite layer as described in any one of claims 1-7; Both the inner and outer surfaces of the bag are coated with a hydrophobic coating. The bag body has a window, and the composite layer is sealed to the window, with the first side facing the inside of the bag and the second side facing the outside of the bag.

9. The modified atmosphere packaging bag according to claim 8, characterized in that: The bag substrate is PE film or PP modified film, and the area of ​​the window accounts for 2%-12% of the total area of ​​the bag.

10. The modified atmosphere packaging bag according to claim 8, characterized in that: The composite layer is connected to the window by heat sealing or adhesive sealing.

Images