Manufacturing method of fresh-keeping cabinet composed of phase-change material and nuclear track membrane

Abstract

The invention discloses a manufacturing method of a fresh-keeping cabinet composed of a phase-change material and a nuclear track membrane, and the manufacturing method comprises the following steps: S1, preparing a plastic box body with a containing cavity which is used for placing articles to be preserved; s2, an interlayer is arranged in the wall body of the plastic box body or an independent phase change material unit is arranged in the containing cavity, and the containing cavity is filled with a paraffin phase change material; s3, according to the size of the plastic box body, one or more ventilation holes of 5-10 cm are formed in the side wall or the top of the plastic box body; and S4, a layer of nuclear track membrane is attached to each vent hole, and the nuclear track membrane has the preset hole diameter and hole density so as to regulate and control the micro-atmosphere environment. By utilizing the latent heat characteristic of the paraffin phase-change material, the temperature in the fresh-keeping cabinet can be kept relatively stable within a certain period of time without an external power supply, energy consumption is remarkably reduced, and the fresh-keeping cabinet belongs to an environment-friendly technology and is particularly suitable for being used in regions with unstable electric power, outdoor operation, short-distance transportation or occasions without power supplies.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, specifically to a method for manufacturing a food preservation cabinet composed of a phase change material and a nucleopore membrane. Background Technology

[0002] With rising living standards and diversified consumption patterns, the freshness and quality of fruits and vegetables have become a key focus for consumers. Traditional methods of preserving fruits and vegetables mainly include low-temperature refrigeration, controlled atmosphere storage (CA), and reduced-pressure storage. Among these, low-temperature refrigeration is the most commonly used method, but it requires continuous electricity consumption, resulting in high operating costs, and it is difficult to maintain a low-temperature environment during power outages or transportation. While controlled atmosphere storage can effectively extend shelf life, it involves complex equipment, high investment costs, and requires precise control of the ambient gases, making it unsuitable for households, small businesses, or short-distance transportation scenarios.

[0003] In recent years, phase change materials (PCMs) have been increasingly applied in food preservation due to their ability to absorb or release large amounts of latent heat during phase change, thus maintaining relatively stable temperatures. Paraffin-based PCMs have become a research hotspot due to their advantages such as good chemical stability, high latent heat value, non-toxicity, odorlessness, and low cost. However, using PCMs alone can only buffer temperature changes to a certain extent. There is a lack of effective active control methods for addressing physiological imbalances and microbial growth caused by the accumulation of ripening gases such as ethylene produced by the respiration of fruits and vegetables, as well as carbon dioxide and water vapor. Therefore, there is still room for improvement in preservation performance.

[0004] Nucleoporous membranes are precision separation membranes formed by chemical etching of polymer films after bombardment with high-energy particles, resulting in uniform cylindrical pores. Their pore size and density can be precisely controlled, exhibiting excellent air permeability, moisture permeability, and selective permeability. Currently, nucleoporous membranes have been applied in some packaging fields, primarily for controlling moisture evaporation or the permeation of specific gases. However, their application in combining with phase change materials to construct integrated, low-cost, passive food storage cabinets has not yet been reported in maturity.

[0005] In addition, existing portable or small-scale preservation devices are mostly simple foam boxes with ice packs, which have problems such as excessive humidity inside the box due to melting ice, large temperature fluctuations, easy cross-contamination, and short shelf life. Moreover, the ice needs to be prepared and carried in advance, which is inconvenient to use.

[0006] Therefore, we propose a method for manufacturing a food storage cabinet composed of phase change materials and nuclear pore membranes. Summary of the Invention

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for manufacturing a food preservation cabinet composed of a phase change material and a nuclear pore membrane, comprising the following steps:

[0008] S1. Prepare a plastic box with a receiving cavity for placing items to be preserved;

[0009] S2. A sandwich layer is provided in the wall of the plastic box or an independent phase change material unit is provided in the cavity, and paraffin-based phase change material is filled into it.

[0010] S3. According to the size of the plastic box, open one or more 5-10cm ventilation holes on its side wall or top;

[0011] S4. A nuclear pore membrane is attached to each of the ventilation holes. The nuclear pore membrane has a preset pore size and pore density to regulate the micro-atmosphere environment.

[0012] S5. Assemble multiple plastic boxes into a complete food storage cabinet using a stacked structure or a pull-out drawer structure.

[0013] Preferably, in step S1, the wall thickness of the plastic box is 3-8 mm.

[0014] Preferably, in step S2, Option 1 (interlayer filling): a hollow interlayer is provided in at least one wall of the plastic box, the volume of the hollow interlayer accounting for 20%-60% of the total volume of the wall; molten paraffin-based phase change material is filled into the hollow interlayer, the filling amount being 80%-95% of the volume of the hollow interlayer, and a phase change energy storage layer is formed after the paraffin cools and solidifies; Option 2 (independent unit): a paraffin pad / paraffin block adapted to the shape of the receiving cavity of the plastic box or detachable is made as a phase change material unit, the latent heat of phase change of the paraffin pad / paraffin block is not less than 150kJ / kg, and the paraffin pad / paraffin block is placed at a preset position at the bottom or side of the receiving cavity, or is made to contact the inner wall surface of the receiving cavity.

[0015] Preferably, in step S2, the phase transition temperature of the paraffin-based phase change material is 0℃-15℃.

[0016] Preferably, in step S3, the spacing between adjacent vents is 1 / 3 to 1 / 2 of the side length of the housing.

[0017] Preferably, in step S4, the material of the nuclear pore membrane is polycarbonate (PC), polyester (PET), or polypropylene (PP).

[0018] Preferably, in step S4, the pore size of the nuclear pore membrane is 0.05-5 μm, and the pore density is 10⁶-10⁻⁶. 10 pcs / cm 2 .

[0019] Preferably, in step S5, the assembly is a stacked type: multiple plastic boxes are stacked and fixed together using slide rails, slots, or bolts to form a multi-layered integrated refrigerator. Alternatively, the assembly is a drawer type: multiple plastic boxes are made into drawer structures with pull-out guide rails and embedded in an integrated refrigerator frame with an insulated outer shell to form a drawer-type integrated refrigerator.

[0020] Preferably, the outer shell of the integrated refrigeration cabinet is made of heat-insulating material.

[0021] Preferably, the inner wall of the plastic box is coated with an antibacterial coating.

[0022] Compared with the prior art, the present invention provides a method for manufacturing a food preservation cabinet composed of phase change material and nuclear pore membrane, which has the following beneficial effects:

[0023] 1. The method for manufacturing a refrigerator composed of this phase change material and a nucleopore membrane utilizes the latent heat properties of the paraffin phase change material to maintain a relatively stable temperature inside the refrigerator for a certain period of time without the need for an external power source. This significantly reduces energy consumption and is a green and environmentally friendly technology. It is particularly suitable for use in areas with unstable power supply, outdoor operations, short-distance transportation, or situations without power. The paraffin phase change material effectively buffers external temperature fluctuations, providing a suitable low-temperature environment for fruits and vegetables. The nucleopore membrane precisely regulates the micro-atmosphere inside the refrigerator, reducing oxygen concentration, appropriately increasing carbon dioxide concentration, and timely removing ethylene and water vapor. This synergistically inhibits the respiration, transpiration, browning reaction, and microbial growth and reproduction of fruits and vegetables. In particular, it can effectively keep leafy greens from turning yellow or losing their flavor within 3-7 days, significantly extending the freshness and shelf life of fruits and vegetables.

[0024] 2. The method for manufacturing this refrigerator, which combines phase change material and a nucleopore membrane, utilizes a plastic casing, paraffin phase change material, and a nucleopore membrane as its main components. The raw materials are widely available, the processing technology is simple, and the manufacturing cost is significantly lower than traditional refrigeration equipment and large controlled atmosphere storage facilities. This facilitates large-scale production and widespread application. A stackable or drawer-style structure can be selected as needed for convenient access to items. Both the paraffin phase change material and the plastic casing are recyclable, and the nucleopore membrane can be processed separately, aligning with the principles of a circular economy. Furthermore, it reduces the use of ice, avoiding the inconvenience and pollution caused by melted water.

[0025] 3. The method for manufacturing a refrigerator composed of this phase change material and a nucleopore membrane allows for precise design and customization of the pore size and pore density of the nucleopore membrane. It can create the most suitable micro-atmosphere environment according to the respiration characteristics and preservation needs of different fruit and vegetable varieties, achieving "intelligent" preservation. It is highly versatile. The paraffin-based phase change material is chemically stable, non-toxic, odorless, and safe to use. The plastic cabinet is lightweight and sturdy, not easily damaged, and the nucleopore membrane also has good physical and chemical stability. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example

[0028] An embodiment of a method for manufacturing a food storage cabinet composed of a phase change material and a core pore membrane.

[0029] A method for manufacturing a food preservation cabinet composed of a phase change material and a nuclear pore membrane includes the following steps:

[0030] S1. Prepare a plastic box with a receiving cavity for placing items to be preserved;

[0031] S2. A sandwich layer is provided in the wall of the plastic box or an independent phase change material unit is provided in the cavity, and paraffin-based phase change material is filled into it.

[0032] S3. According to the size of the plastic box, open one or more 5-10cm ventilation holes on its side wall or top;

[0033] S4. A nuclear pore membrane is attached to each of the ventilation holes. The nuclear pore membrane has a preset pore size and pore density to regulate the micro-atmosphere environment.

[0034] S5. Assemble multiple plastic boxes into a complete food storage cabinet using a stacked structure or a pull-out drawer structure.

[0035] Specifically, in step S1, the wall thickness of the plastic box is 3-8mm.

[0036] Specifically, in step S2, Option 1 (interlayer filling): A hollow interlayer is provided in at least one wall of the plastic box, the volume of which accounts for 20%-60% of the total volume of the wall; molten paraffin-based phase change material is filled into the hollow interlayer, the filling amount being 80%-95% of the volume of the hollow interlayer, and a phase change energy storage layer is formed after the paraffin cools and solidifies; Option 2 (independent unit): A paraffin pad / paraffin block adapted to the shape of the cavity of the plastic box or detachable is made as a phase change material unit, the latent heat of phase change of the paraffin pad / paraffin block is not less than 150kJ / kg, and the paraffin pad / paraffin block is placed at a preset position at the bottom or side of the cavity, or made to contact the inner wall surface of the cavity.

[0037] Specifically, in step S2, the phase transition temperature of the paraffin-based phase change material is 0℃-15℃.

[0038] Specifically, in step S3, the spacing between adjacent vents is 1 / 3 to 1 / 2 of the side length of the box.

[0039] Specifically, in step S4, the material of the nuclear pore membrane is polycarbonate (PC), polyester (PET), or polypropylene (PP).

[0040] Specifically, in step S4, the pore size of the nuclear pore membrane is 0.05-5 μm, and the pore density is 10. 6 -1010 pieces / cm 2 .

[0041] Specifically, in step S5, the stacked assembly involves stacking multiple plastic boxes together using slide rails, slots, or bolts to form a multi-layered integrated refrigerator. Alternatively, the drawer-type assembly involves fabricating multiple plastic boxes into drawer structures with pull-out guide rails and embedding them into an integrated refrigerator frame with an insulated outer shell, forming a drawer-type integrated refrigerator.

[0042] Specifically, the outer shell of the refrigerated display case is made of heat-insulating material.

[0043] Specifically, the inner wall of the plastic box is coated with an antibacterial coating.

[0044] Through the above technical solution, this invention utilizes the latent heat properties of paraffin phase change material to maintain a relatively stable temperature inside the refrigerator for a certain period of time without an external power source, significantly reducing energy consumption. This is a green and environmentally friendly technology, particularly suitable for areas with unstable power supply, outdoor operations, short-distance transportation, or situations without power. The paraffin phase change material effectively buffers external temperature fluctuations, providing a suitable low-temperature environment for fruits and vegetables. The nucleopore membrane precisely regulates the micro-atmosphere inside the refrigerator, reducing oxygen concentration, appropriately increasing carbon dioxide concentration, and promptly removing ethylene and water vapor. This synergistically inhibits respiration, transpiration, browning reactions, and microbial growth and reproduction in fruits and vegetables, especially effectively preventing leafy greens from turning yellow or losing flavor within 3-7 days, significantly extending the freshness and shelf life of fruits and vegetables. By using a plastic box, paraffin phase change material, and nucleopore membrane as the main components, the raw materials are widely available, the processing technology is simple, and the manufacturing cost is far lower than traditional refrigeration equipment and large controlled atmosphere storage facilities, facilitating large-scale production and widespread application. A stacked or drawer-type structure can be selected as needed for convenient access to items. Both the paraffin phase change material and the plastic container are recyclable and reusable, and the nucleopore membrane can be processed separately, aligning with the concept of a circular economy. Simultaneously, it reduces the use of ice, avoiding the inconvenience and pollution caused by meltwater. The pore size and density of the nucleopore membrane can be precisely designed and customized, creating the optimal micro-atmosphere environment based on the respiration characteristics and preservation needs of different fruit and vegetable varieties, achieving "intelligent" preservation. It is highly versatile; the paraffin-based phase change material is chemically stable, non-toxic, odorless, and safe to use; the plastic container is lightweight and sturdy, not easily damaged, and the nucleopore membrane also possesses good physicochemical stability.

[0045] Example 1: Construction of a stackable leafy green vegetable preservation cabinet

[0046] S1. Box Selection and Pre-treatment: Food-grade PP plastic sheets are used to manufacture individual rectangular plastic boxes with dimensions of 40cm × 30cm × 25cm (length × width × height) and a wall thickness of 5mm. The interior of the box forms a cavity for holding leafy green vegetables.

[0047] S2. Phase Change Material Filling (Layered Filling Scheme): Hollow layers are formed within the four side walls and bottom wall of the plastic box through secondary injection molding or bonding, with a layer thickness of approximately 10mm. The total volume of the single box wall layer is calculated to be approximately (40*25*1+30*25*1)²+40*30*1=(1000+750)²+1200=3500+1200=4700cm³ 3 The interlayer volume, calculated at 50%, is approximately 2350 cm². 3 Paraffin wax with a melting point of 5°C (latent heat of phase change of approximately 200 kJ / kg) was heated to a molten state and injected into the aforementioned hollow interlayer, filling it to 90% of its volume (approximately 2115 cm³). 3 The paraffin wax is allowed to cool and solidify naturally, forming a phase change energy storage layer. The amount of paraffin wax used is approximately 0.9 g / cm³. 3 Multiply by the volume, i.e., 2115cm³ 3 *0.9g / cm 3 ≈1903g.

[0048] S3. Ventilation Hole Installation: On the upper part of the two opposite side walls of each plastic box, a circular ventilation hole with a diameter of 8cm is installed. The distance between the two holes is about 1 / 2 (15cm) of the box width of 30cm.

[0049] S4. Nuclear pore membrane bonding: A nuclear pore membrane made of polycarbonate (PC) is selected, with a pore size of 0.2 μm and a pore density of 5 × 10⁻⁶. 8 pcs / cm 2 (These parameters are optimized for the respiration characteristics of leafy green vegetables, and can moderately reduce O2, increase CO2, and release ethylene.) Cut the core pore membrane into a circle slightly larger than the diameter of the vent holes, and use food-grade adhesive to tightly attach it to the outer surface of each vent hole to ensure good sealing and air permeability.

[0050] S5. Assembled Refrigerated Display Case (Layered): Construct a metal frame as the outer shell of the refrigerated display case, with multiple support panels inside. Secure the five plastic boxes prepared above to the support panels using slots, forming a five-layer stacked structure. Fill the gaps between the layers with a small amount of polyurethane foam scraps as insulation. The exterior of the refrigerated display case can be wrapped with an insulating canvas or thin sheet metal shell to further enhance the insulation effect.

[0051] Usage Test: Freshly picked spinach, after being derooted, washed, and drained, was placed in the refrigerated display case prepared in this embodiment and in an untreated ordinary plastic box of the same size, both at room temperature (25°C). The degree of yellowing and sensory quality of the spinach were observed and recorded daily. The results showed that the spinach in the ordinary plastic box began to show obvious yellowing on the second day, and by the fourth day, the yellowing was severe, rendering it unmarketable. In contrast, the spinach in the refrigerated display case prepared in this embodiment maintained its bright green color on the seventh day, with no obvious wilting or off-odors, and its shelf life was significantly extended. No obvious condensation or water accumulation was observed during the process.

[0052] Example 2: Manufacturing of a drawer-type multi-variety fruit and vegetable preservation cabinet

[0053] S1. Box Selection and Pre-treatment: Several drawer-type plastic boxes of different sizes are made of food-grade ABS plastic. For example, box A (30cm×20cm×15cm) is used to store strawberries, box B (40cm×30cm×20cm) is used to store apples, and box C (35cm×25cm×18cm) is used to store lettuce. The wall thickness of all boxes is 6mm.

[0054] S2. Phase Change Material Configuration (Independent Unit Scheme): For strawberries (suitable low temperature 0-2℃), use paraffin wax flakes with a melting point of 2℃; for apples (suitable low temperature 0-4℃) and lettuce (suitable low temperature 0-5℃), use paraffin wax blocks with a melting point of 3℃. Fabricate the paraffin wax flakes / blocks into tray-shaped paraffin wax pads that fit the shape of the bottom of the corresponding chamber. The latent heat of phase change of each paraffin wax pad should not be less than 180kJ / kg. Place the paraffin wax pad for chamber A at the bottom of chamber A, and place the paraffin wax pads for chambers B and C into the pre-set grooves on the side of their respective chambers.

[0055] S3. Ventilation openings: Box A has a 6cm diameter vent at the top; Box B has two symmetrical 7cm diameter vents on the upper side wall; Box C has an 8cm diameter vent at the top.

[0056] S4. Nuclear pore membrane bonding: The vent holes in box A have a pore size of 0.1 μm and a pore density of 1×10⁻⁶. 9 pcs / cm 2 PET core-pore membranes (strawberries have high respiration rates, requiring stricter gas control); Box B uses 0.3μm pore size and 3×10⁻⁶ pore density membranes. 8 pcs / cm 2 PC nuclear pore membrane; C-box uses a pore size of 0.2 μm and a pore density of 5 × 10⁻⁶. 8 pcs / cm 2 The PC core pore membranes all employ an inner-side bonding method and are reinforced with sealing rings.

[0057] S5. Assembly of the Complete Refrigerated Display Case (Drawer Type): Construct a horizontal insulated outer shell similar to a household refrigerator, with multiple drawer slides inside. Install the drawer slides onto the three sizes of plastic boxes (A, B, and C) mentioned above, allowing them to be pushed into different positions within the insulated outer shell as independent drawers. The insulated outer shell uses a polyurethane foam insulation layer with a thickness of no less than 3cm. The front of the outer shell features a transparent observation window and individual handles for each drawer.

[0058] Usage test: Place the corresponding fruits and vegetables in each drawer and close the cabinet doors. After 5 days at room temperature (30℃), the strawberries remained bright red and plump, without mold or rot; the apples had a moderate firmness and a crisp, sweet taste; and the lettuce leaves were vibrant green, without yellowing or wilting. The paraffin pads can be removed and recycled, and the cabinet can be reused after cleaning.

[0059] Example 3: Manufacturing of a Portable Express Delivery Refrigerated Box

[0060] S1. Box Selection and Pre-treatment: High-strength, lightweight food-grade HDPE plastic is used to mold a single square plastic box with dimensions of 50cm×40cm×35cm, wall thickness of 8mm, and a sealable lid on top.

[0061] S2. Phase change material filling (mainly sandwich filling, supplemented by independent units): All six walls of the enclosure are equipped with hollow sandwich layers, with the sandwich layer volume accounting for approximately 40% of the total wall volume. The filling material is a paraffin wax mixture with a melting point of 5°C (with a small amount of thickener added to prevent leakage), with a filling rate of 90%. At the same time, a large-sized paraffin wax brick is fixed in the center of the inner side of the enclosure lid as a supplementary phase change unit.

[0062] S3. Ventilation hole opening: A square ventilation hole with a diameter of 10cm is opened in the middle of the two opposite side walls of the box.

[0063] S4. Nuclear pore membrane bonding: A nuclear pore membrane made of polypropylene (PP) with a pore size of 0.4 μm and a pore density of 2 × 10⁻⁶ is selected. 8 pcs / cm 2 Cut it to the size that matches the square vent hole, and seal it with waterproof tape to the inner surface of the vent hole.

[0064] S5. Overall Form: This embodiment is a single box, which can be used directly as a portable express delivery cooler, or multiple boxes can be stacked as needed. Handles and an insulated cover can be added to the outside of the box.

[0065] Usage test: In a simulated summer express delivery environment (external temperature 35℃), after sealing the insulated box containing various fresh fruits and vegetables, the internal temperature of the box remained between 6-8℃ after 48 hours, indicating that the fruits and vegetables were still fresh. The core membrane effectively prevented excessive condensation of water vapor and the entry of external pollutants.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a food preservation cabinet composed of a phase change material and a nuclear pore membrane, characterized in that: The method comprises the following steps: S1, preparing a plastic box body with a containing cavity for placing fresh-keeping objects; S2, arranging a sandwich or an independent phase change material unit in the wall of the plastic box body or in the containing cavity, and filling paraffin phase change material therein; S3, according to the size of the plastic box body, one or more 5-10 cm air holes are arranged on the side wall or top of the plastic box body; S4, a nuclear pore membrane with a preset pore size and pore density is attached to each air hole to regulate the micro-atmosphere environment; S5, a plurality of plastic box bodies are assembled into an integrated fresh-keeping cabinet through a laminated structure or a pull-out drawer structure.

2. The method for making a fresh food storage cabinet of claim 1, wherein: In the step S1, the wall thickness of the plastic box body is 3-8 mm.

3. The method of claim 1, wherein the method further comprises: In the step S2, scheme one (sandwich filling): a hollow sandwich is arranged in at least one wall of the plastic box body, and the volume of the hollow sandwich accounts for 20%-60% of the total volume of the wall; the hollow sandwich is filled with molten paraffin phase change material, and the filling amount is 80%-95% of the volume of the hollow sandwich, and after the paraffin cools and solidifies, a phase change energy storage layer is formed; scheme two (independent unit): a paraffin pad / paraffin block that is shaped to fit or detachable from the containing cavity of the plastic box body is made as a phase change material unit, and the latent heat of phase change of the paraffin pad / paraffin block is not less than 150 kJ / kg, and the paraffin pad / paraffin block is placed at a preset position at the bottom or side of the containing cavity or in contact with the inner wall of the containing cavity. ​ 4. The method for making a fresh food storage cabinet of claim 1, wherein: In the step S2, the phase change temperature of the paraffin phase change material is 0-15℃.

5. The method of claim 1, wherein the method further comprises: In the step S3, the spacing between adjacent air holes is 1 / 3 to 1 / 2 of the side length of the box body. ​ 6. The method of claim 1, wherein the method further comprises: In the step S4, the material of the nuclear pore membrane is polycarbonate (PC), polyester (PET) or polypropylene (PP). ​ 7. The method of claim 1, wherein the method further comprises: providing a plurality of nucleopore membranes; and providing a plurality of phase change materials; and placing the plurality of nucleopore membranes and the plurality of phase change materials in the chamber. The pore size of the nuclear pore membrane is 0.05-5 μm, and the pore density is 106-10 10 9 / cm 2 .

8. The method of claim 1, wherein the method further comprises: providing a plurality of nanometer-sized pores in the phase change material; and providing a plurality of nanometer-sized pores in the nanometer-sized pore film. In the step S5, laminated assembly: a plurality of plastic box bodies are fixed by sliding rail, clamping groove or bolt connection method, forming a multi-layer structure integrated fresh-keeping cabinet. Alternatively, drawer assembly: a plurality of plastic box bodies are made into a drawer structure with a pull-out guide rail, and are embedded into an integrated fresh-keeping cabinet frame with a heat-insulating shell, forming a drawer integrated fresh-keeping cabinet.

9. The method of claim 1, wherein the method further comprises: The shell of the integrated fresh-keeping cabinet is made of heat-insulating material. ​ 10. The method of claim 1, wherein the method further comprises: The inner wall of the plastic box body is coated with an antibacterial coating. ​