Preparation process of cold-chain logistics insulation box and insulation box

Abstract

This invention discloses a manufacturing process for a cold chain logistics insulated box and the insulated box thereof, belonging to the field of insulation materials. This invention achieves a synergistic improvement in the thermal conductivity, flexibility, energy storage density, and reliability of cold chain logistics cold storage materials by constructing an expanded graphite-sodium polyacrylate dual-network composite structure. Using a combination of vacuum impregnation and in-situ polymerization, a flexible sodium polyacrylate polymer network is constructed within the three-dimensional thermally conductive skeleton of expanded graphite, forming a rigid-flexible interpenetrating dual-network structure. By controlling the type of phase change material (water-based or eutectic salt system) and the composition of the dual network, the phase change temperature can be precisely adjusted within the range of -21°C to 0°C, covering the full temperature range requirements of fresh food preservation, pharmaceutical cold chain, and cryogenic freezing. The water-based system is suitable for short-term, high-frequency, and cost-sensitive scenarios; the eutectic salt system is suitable for long-term, high-temperature challenges, and high-reliability scenarios, forming a complementary technical solution.

Description

Technical Field

[0001] This invention discloses a thermal insulation material, and in particular relates to a manufacturing process for a cold chain logistics thermal insulation box and the thermal insulation box thereof. Background Technology

[0002] Traditional cold chain distribution methods mainly use foam boxes combined with ice packs. This method is not only inefficient and costly, but also environmentally unfriendly, making it difficult to meet the modern cold chain distribution needs that are dominated by small batches, multiple varieties, multiple shipments, and high freshness.

[0003] Phase change materials (PCCs), as a highly efficient energy storage medium, can absorb or release a large amount of latent heat during phase change, maintaining a constant temperature, and have broad application prospects in cold chain insulation boxes. However, traditional PCCs have many drawbacks in practical applications: first, severe phase separation occurs, leading to a decrease in cold storage performance; second, the degree of supercooling is large, which is not conducive to actual temperature control; third, they are prone to leakage in liquid state, contaminating goods; and fourth, they have low thermal conductivity, resulting in slow heat transfer. Summary of the Invention

[0004] The purpose of this invention is to provide a manufacturing process for a cold chain logistics insulated box and the insulated box thereof in order to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a process for manufacturing insulated boxes for cold chain logistics, comprising the following steps:

[0006] S1, Preparation of phase change cold storage materials

[0007] (1) Expanded graphite was pressed into a material with a density of 0.1 g / cm³. 3 Construct a three-dimensional thermally conductive framework from the bulk material:

[0008] The preparation of modified expanded graphite includes the following steps:

[0009] For pretreatment, polyvinylpyrrolidone (PVP) was dissolved in deionized water, and expanded graphite (EG) was added. The mass ratio of EG to PVP was 3:1. The mixture was stirred at 600 r / min for 1 h at room temperature. After filtration and washing, it was dried at 80°C for 12 h to obtain pretreated expanded graphite.

[0010] In-situ growth was performed by adding pretreated expanded graphite and tetraethyl orthosilicate to anhydrous ethanol at a mass-to-volume ratio of 6 g:35 mL, ultrasonicating for 5 min, transferring to a 40°C water bath, adding 30 wt% ammonia solution while stirring at 300 r / min, reacting for 6 h, filtering and washing, and drying at 60°C for 12 h to obtain SiO2-modified expanded graphite, wherein the mass loading of SiO2 was 7 wt%.

[0011] (2) Preparation of precursor solution: Sodium acrylate monomer, crosslinking agent N,N'-methylenebisacrylamide and initiator ammonium persulfate are dissolved in deionized water, wherein the concentration of sodium acrylate is 15wt%, the mass ratio of crosslinking agent to sodium acrylate is 1:15, and the mass ratio of initiator to sodium acrylate is 1:4.

[0012] (3) The modified expanded graphite block was placed in the precursor solution and immersed for 2 hours under a vacuum of 0.1-0.2 atm;

[0013] (4) The impregnated block was transferred to a 50°C hot air chamber for in-situ polymerization reaction for 10 h to obtain a modified expanded graphite-sodium polyacrylate dual network carrier.

[0014] (5) Secondary water absorption process: the phase change material is deionized water. The modified expanded graphite-sodium polyacrylate double network carrier is soaked in deionized water for 12 hours. H2O is loaded into the expanded graphite-sodium polyacrylate double network and the mass fraction of H2O is 80% to obtain a shaped composite phase change cold storage material.

[0015] S2, Cold Storage Box Assembly

[0016] The outer and inner boxes are made of foamed polypropylene material. The inner wall of the inner box is grooved around the perimeter. The shaped composite phase change cold storage material prepared in step S1 is cut into suitable cold storage sheets. After the cold storage sheets are pre-cooled, an aluminum-plastic composite film is wrapped around the surface of the cold storage sheets. Thermally conductive silicone pads are attached to the grooves. The cold storage sheets and the inner box form a tight thermal contact through the thermally conductive silicone pads. The outer and inner boxes are assembled to obtain the cold chain logistics insulated box.

[0017] As a preferred option, the secondary water absorption in (5) of S1 is replaced by vacuum impregnation melt blending method, in which the phase change material and the modified expanded graphite-sodium polyacrylate dual network carrier are mixed at a mass ratio of 80:20, heated until the phase change material melts, impregnated under a vacuum of 0.08MPa for 20min, with stirring during the process, and then cooled and shaped to obtain a shaped composite phase change cold storage material.

[0018] The phase change material is a ternary eutectic salt of Na2SO4·10H2O-MgSO4·7H2O-water, and its preparation includes the following steps:

[0019] Na2SO4·10H2O, MgSO4·7H2O and deionized water (H2O) were mixed in a mass ratio of 1:4:5 and heated to complete melting under magnetic stirring at a speed of 300 r / min until the solution became clear and transparent, thus obtaining the phase change material.

[0020] Preferably, in S1, the expanded graphite has a particle size of 100 mesh.

[0021] A cold chain logistics insulated box includes a cold chain logistics insulated box body manufactured by the above-mentioned cold chain logistics insulated box body manufacturing process. The cold chain logistics insulated box body includes an outer box body, an inner box body, and a cold storage sheet. The cold storage sheet is a double-network shaped composite phase change cold storage material. The phase change material is loaded in the pores of the double-network carrier. The cold storage sheet is detachably disposed in the slots around the inner wall of the inner box body.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] By constructing a dual-network composite structure of expanded graphite and sodium polyacrylate, a synergistic improvement in thermal conductivity, flexibility, energy storage density, and reliability of cold chain logistics cold storage materials was achieved. A combination of vacuum impregnation and in-situ polymerization was used to construct a flexible sodium polyacrylate network within the three-dimensional thermally conductive framework of expanded graphite, forming a rigid-flexible interpenetrating dual-network structure. This structure enhances the tensile and flexural strength of the composite material through topological entanglement and interfacial anchoring, while maintaining high thermal conductivity. The porous structure of expanded graphite provides non-uniform nucleation sites for phase change materials, while the hydrophilic functional groups of the sodium polyacrylate network induce heterogeneous nucleation, synergistically reducing phase change supercooling. The nano-confinement effect of the dual network inhibits grain coarsening and phase separation. After multiple thermal cycles, the phase change enthalpy retention rate remains at a high level. This technology solves the problem of cyclic failure in hydrated salt phase change materials. Through a secondary water absorption process or vacuum melt impregnation, the sodium polyacrylate network anchors the phase change medium through hydrogen bonding, ion hydration, and capillary action. Combined with the physical adsorption of expanded graphite, it achieves shape fixation without leakage, reduces the mass loss rate, and improves performance compared to traditional physically adsorbed composite materials. Modular cold storage blocks, combined with thermally conductive interface materials, form an enclosed thermal management structure. By controlling the type of phase change material (water-based or eutectic salt system) and the composition of the dual network, the phase change temperature can be precisely adjusted within the range of -21°C to 0°C, covering the full temperature range requirements of fresh food preservation, pharmaceutical cold chain, and cryogenic freezing. The water-based system is suitable for short-term, high-frequency, and cost-sensitive scenarios, while the eutectic salt system is suitable for long-term, high-temperature challenges and high-reliability scenarios, forming a complementary technical solution. Attached Figure Description

[0024] Figure 1 A chart comparing phase change performance;

[0025] Figure 2 A chart comparing thermal conductivity;

[0026] Figure 3 A chart comparing mechanical properties;

[0027] Figure 4 A chart comparing the time to complete cooling;

[0028] Figure 5 A chart comparing heat preservation time and temperature uniformity;

[0029] Figure 6 A comparison chart showing the uniformity of temperature distribution. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. In this description, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "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 the present 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 the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0031] A process for manufacturing insulated boxes for cold chain logistics includes the following steps:

[0032] S1, Preparation of phase change cold storage materials

[0033] (1) Expanded graphite was pressed into a material with a density of 0.1 g / cm³. 3 Construct a three-dimensional thermally conductive framework from the bulk material:

[0034] The preparation of modified expanded graphite includes the following steps:

[0035] For pretreatment, polyvinylpyrrolidone (PVP) was dissolved in deionized water, and expanded graphite (EG) was added. The mass ratio of EG to PVP was 3:1. The mixture was stirred at 600 r / min for 1 h at room temperature. After filtration and washing, it was dried at 80°C for 12 h to obtain pretreated expanded graphite.

[0036] In-situ growth was performed by adding pretreated expanded graphite and tetraethyl orthosilicate to anhydrous ethanol at a mass-to-volume ratio of 6 g:35 mL, ultrasonicating for 5 min, transferring to a 40°C water bath, adding 30 wt% ammonia solution while stirring at 300 r / min, reacting for 6 h, filtering and washing, and drying at 60°C for 12 h to obtain SiO2-modified expanded graphite, wherein the mass loading of SiO2 was 7 wt%.

[0037] In S1, the expanded graphite has a particle size of 100 mesh. Expanded graphite (EG) is produced by intercalating natural graphite with a strong oxidant and instantaneously expanding it at a high temperature of 900-1000°C. The graphite sheets expand tens to hundreds of times along the c-axis, forming a loose and porous worm-like morphology. Numerous slit-like pores are formed between the sheets, with the pore size distribution mainly consisting of mesopores of 2-50 nm and macropores of >50 nm. The specific surface area reaches 10-30 m². 2 / g, under external force, worm-like particles interlock and align in a lamellar orientation, forming a surface-to-surface contact heat-conducting network with a density of 0.1g / cm³. 3 With a porosity of approximately 95%, it retains sufficient space to accommodate subsequent polymers and phase change materials. The high intrinsic thermal conductivity of EG sheets (2000 W / (m·K)) provides a rapid thermal conduction channel for the composite material, while the macropores are used to store the phase change material and the mesopores are used to anchor the polymer molecular chains.

[0038] (2) Preparation of precursor solution: Sodium acrylate monomer, crosslinking agent N,N'-methylenebisacrylamide and initiator ammonium persulfate are dissolved in deionized water, wherein the concentration of sodium acrylate is 15wt%, the mass ratio of crosslinking agent to sodium acrylate is 1:15, and the mass ratio of initiator to sodium acrylate is 1:4.

[0039] Sodium acrylate is a hydrophilic monomer containing -COO. - Na + The groups, after polymerization, form a high molecular weight electrolyte chain. The crosslinking agent N,N'-methylenebisacrylamide is a bifunctional monomer, with two C=C double bonds connecting different polymer chains to form three-dimensional crosslinking points. Ammonium persulfate is a thermal initiator, decomposing at 50°C to produce SO4. - Free radicals initiate chain polymerization;

[0040] (3) The modified expanded graphite block was placed in the precursor solution and immersed for 2 hours under a vacuum of 0.2 atm;

[0041] Air is extracted from the EG pores, and the number of gas molecules is reduced by 80% at 0.2 atm. Under normal pressure, the precursor solution rapidly penetrates under the pressure difference between the external atmospheric pressure and the negative pressure of the pores. Sodium acrylate forms hydrogen bonds with the -OH and -COOH groups on the EG surface, promoting wetting.

[0042] (4) The impregnated block was transferred to a 50°C hot air chamber for in-situ polymerization reaction for 10 h to obtain a modified expanded graphite-sodium polyacrylate dual network carrier.

[0043] Chain trigger: ;

[0044] ;

[0045] Chain growth:

[0046] ;

[0047] Chain crosslinking:

[0048] ;

[0049] Under the synergistic effect of the dual-network system, sodium polyacrylate (PAAS) chains pass through the narrow gaps between EG layers, forming a mechanical interlock. The -COO of the PAAS... - The PAAS network forms ionic and hydrogen bonds with oxygen-containing groups on the EG surface. Under external force, the PAAS network absorbs energy through segment slip and conformational changes, protecting the EG backbone from fragmentation. The -COO groups of the PAAS... - Na + The functional groups transform the hydrophobic EG into a hydrophilic surface, creating conditions for subsequent water loading;

[0050] (5) When the first water-absorbing PAAS network is formed in situ, it already contains water from the precursor solution, and the network is in a swollen state at this time.

[0051] Route a: When deionized water is used as the phase change material, a secondary water absorption process is employed. The modified expanded graphite-sodium polyacrylate dual-network carrier is immersed in deionized water for 12 hours. H2O is loaded into the expanded graphite-sodium polyacrylate dual network, with an H2O mass fraction of 80%, resulting in a shaped composite phase change cold storage material. Osmotic pressure serves as the driving force, PAAS is a high-concentration polyelectrolyte network, and the external water generates an osmotic pressure difference. + and H + Ion exchange enhances the electrostatic repulsion of the PAAS chains, causing the network to expand. The expanded network further compresses the EG sheets, while simultaneously absorbing a large amount of water into the newly formed pores.

[0052] H2O forms hydrogen bonds with -COOH and -OH of PAAS, inhibiting flow. Hydration binds H2O molecules around the ions. Capillary forces in the mesopores prevent liquid water leakage. The rubber elasticity of the cross-linked network restricts the macroscopic migration of water molecules. After secondary water absorption, the water content and enthalpy value increase.

[0053] Route b: When the phase change material is a ternary eutectic salt of Na2SO4·10H2O-MgSO4·7H2O-water, its preparation includes the following steps:

[0054] Na2SO4·10H2O, MgSO4·7H2O and deionized water H2O were mixed in a mass ratio of 1:4:5 and heated to 60℃ under magnetic stirring at a stirring speed of 300 r / min until completely melted and the solution became clear and transparent, thus obtaining a phase change material.

[0055] The phase change material and the modified expanded graphite-sodium polyacrylate dual network carrier were mixed at a mass ratio of 80:20 using a vacuum impregnation melt blending method. The mixture was heated until the phase change material melted, and then impregnated under a vacuum of 0.08 MPa for 20 minutes with stirring during the process. After cooling and shaping, the shaped composite phase change cold storage material was obtained.

[0056] High concentration of Mg 2+ An ion bridging effect is generated, Mg 2+ As a divalent cation, it can react with two -COO groups simultaneously. - Coordination: -COO - …Mg 2+ …-COO - Physical cross-linking points are formed; high concentration of Mg 2+ It has a charge shielding effect, high ionic strength compresses the electric double layer, and reduces -COO - Electrostatic repulsion occurs between Mg and Mg, causing the chain conformation to change from an extended state to a coiled state, and the solution viscosity decreases; 2+ Strong hydration capacity and AAS's -COO - Competition for water molecules affects polymerization kinetics;

[0057] Ion bridging dynamic equilibrium:

[0058] ;

[0059] Reversible physical cross-linking is formed, the network exhibits self-healing and ion-responsive properties, and the final network structure includes a permanent covalent network framework formed by chemical cross-linking of N,N'-methylenebisacrylamide and ion-crosslinked Mg 2+ The dynamic physical network formed by bridging;

[0060] Vacuum impregnation melt blending: The preheating section (40°C, 10 min) completely melts the eutectic salt, causing ion hydrates to dissociate and form a homogeneous liquid phase; the vacuum infusion section (0.08 MPa, 20 min) removes pore gases and promotes melt penetration. Driven by the pressure difference, the melt fills the pores of EG-PAAS, and the ions react with the -COO groups of PAAS. - Coordination occurs, forming a pre-organized structure; a pressure holding section (0.1 MPa, 20 min) ensures complete filling and eliminates air bubbles;

[0061] The melt rises in the capillary, reaching equilibrium distribution and increasing density. A controlled cooling section (1-2°C / min to -10°C, then natural cooling) guides eutectic crystallization, preventing overcooling and phase separation. The PAAS network acts as a template, inducing heterogeneous nucleation, with Na₂SO₄·10H₂O and MgSO₄·7H₂O crystallizing synergistically. The dual network creates a confinement effect on the eutectic salt; the nanopores divide the melt into isolated microregions, eliminating macroscopic convection and preventing density-driven stratification. 2-With EG surface positive electrical defects, Mg 2+ With -COO - Coordination, PAAS's -COO - Competition for water molecules reduces water activity. w To suppress the preferential crystallization of Na2SO4·10H2O, the heterogeneous interface simultaneously satisfies Na + and Mg 2+ The hydration structure requires promoting true eutectic nucleation, rather than stepwise crystallization;

[0062] S2, Cold Storage Box Assembly

[0063] The outer and inner boxes are made of foamed polypropylene material. Grooves are created around the inner wall of the inner box. The shaped composite phase change cold storage material prepared in step S1 is cut into suitable cold storage sheets. After pre-cooling, an aluminum-plastic composite film is wrapped around the surface of the cold storage sheets. Thermally conductive silicone pads are attached to the grooves, forming a tight thermal contact between the cold storage sheets and the inner box through the thermally conductive silicone pads. Assembling the outer and inner boxes yields the insulated box for cold chain logistics. Standardized modules are cut to size and matched to the box structure, facilitating recycling and reuse, thus achieving the recycling of the cold storage sheets and the aluminum-plastic composite film. Physical isolation is provided to prevent surface contamination, maintain the purity of the phase change material, and extend its service life. Thermally conductive silicone pads fill the interface gaps and reduce contact thermal resistance. Compared with the traditional central arrangement, which results in uneven temperature distribution and high thermal resistance in the edge area, the four-wall arrangement forms a cold storage wall for enclosed temperature control. The heat flow path is optimized: external heat intrusion → is quickly absorbed by the nearest C-PCM cold storage sheet → the high thermal conductivity of the dual network allows the heat to be quickly dispersed to the entire cold storage sheet → latent heat of phase change is absorbed, and the temperature remains constant → the flexibility of the PAAS network allows the cold storage sheet to fit tightly with the box wall, reducing contact thermal resistance.

[0064] A comparative experiment was conducted on the design systems of water-based H2O@EG-PAAS and eutectic salt@EG-PAAS. A complete evaluation system was established, covering material preparation, performance characterization, and application scenario verification. The applicable boundaries of each system were clarified. The sample codes and formulations are shown in Table 1 below.

[0065] Table 1, Sample Codes and Formulations

[0066] ;

[0067] Experiment 1: Comparison of Phase Transition Behavior (DSC Test)

[0068] Experimental Design:

[0069] Instrument: Differential Scanning Calorimeter TAQ20

[0070] Program: -30°C → 30°C, rate 2°C / min, N2 atmosphere

[0071] Samples: 5-10 mg each of A-10, B-4, and C-PCM;

[0072] The results are as follows Figure 1 As shown, the characteristics of a water-based system are:

[0073] Sharp peak shape: pure water phase transition, single nucleation site, EG pores;

[0074] High enthalpy: Water content >85% after secondary water absorption;

[0075] Slight supercooling: heterogeneous nucleation of EG is effective;

[0076] Characteristics of eutectic salt systems:

[0077] Possible peak splitting: Incomplete eutectic behavior of Na2SO4·10H2O and MgSO4·7H2O;

[0078] Decreased enthalpy: Increased carrier mass fraction, higher inorganic salt density;

[0079] Moderate supercooling: PAAS network induces nucleation, but increased ionic complexity creates kinetic barriers;

[0080] Experiment 2: Comparison of thermal conductivity (HotDisk method)

[0081] Experimental Design:

[0082] Probe: TPS2500;

[0083] Sample: Pressed into a φ30×5mm round disc;

[0084] Temperature: 25°C (solid state) and above the phase transition temperature (liquid state);

[0085] The results are as follows Figure 2 As shown, the thermal conductivity ranking is: C-EG > A-10 > B-4 > B-15 > pure PCM;

[0086] Water-based salts are superior to eutectic salts because H2O molecules are small, resulting in low interfacial thermal resistance, and the ions increase phonon scattering. Low-temperature salts have even lower thermal conductivity and may form amorphous or glassy regions. PAAS reduces thermal conductivity. The polymer has low intrinsic thermal conductivity, but it is a necessary component of the system.

[0087] Experiment 3: Mechanical Behavior Test

[0088] Test items:

[0089] Compressive strength: Compression testing machine, standard ASTM D695, speed 2 mm / min;

[0090] Three-point bending: span 60mm, speed 1mm / min;

[0091] Dynamic mechanical analysis (DMA): -50 to 50°C, 1 Hz;

[0092] The results are as follows Figure 3 As shown, the reason why the eutectic salt system is more rigid is that the inorganic salt grains act as rigid filling phases, increasing the modulus, and Mg... 2+ Bridged ionic crosslinking enhances the PAAS network, but increases brittleness and reduces fracture strain; the reason why water-based systems are more flexible is that water acts as a plasticizer, lowering the glass transition temperature. The PAAS network is highly swollen, with entropic elasticity dominating, making it suitable for scenarios requiring bending deformation.

[0093] Experiment 4: Cooling Storage and Release Dynamics

[0094] Experimental setup:

[0095] ;

[0096] Temperature monitoring system:

[0097] ;

[0098] Thermocouple specifications: Type K, diameter 0.5mm, accuracy ±0.1°C, response time <0.5s;

[0099] Simulated cargo: 800g of salt water solution, mass fraction 8.5% NaCl, phase change temperature about -21°C, representing actual cold chain cargo such as vaccines, fresh food, blood plasma and other temperature sensitive products, which do not undergo phase change within the test temperature range, only sensible heat change;

[0100] Container: Food-grade PE sealed bag, dimensions 150mm×100mm×50mm;

[0101] The test sample configuration is shown in Table 2 below:

[0102] Table 2, Test Sample Configuration

[0103] ;

[0104] Both the sample and the cold storage sheet were pre-cooled in a -20°C refrigerator for 12 hours. The surface temperature after pre-cooling was recorded. The constant temperature chamber was initially set to -20°C. It was stopped when the center T1 inside the chamber dropped to -15°C. The cooling curve was recorded, and the time to reach -15°C was marked. The temperature was then maintained at -20°C for a total pre-cooling time of 12 hours to confirm that the cold storage sheet was completely cured.

[0105] Transfer the insulated box to a constant temperature box, set it to 25°C, and continuously record the temperature changes until the temperature T1 inside the box rises to 8°C (medical standard) or 15°C (fresh food standard). Record the temperature difference between T1 and T8 at each point and calculate the standard deviation σ.

[0106] like Figure 4 As shown, the complete cold storage time for water-based A-10 is 100 min, for eutectic salt B-4 it is 110 min, and for commercial ice packs it is 120 min; Figure 5 As shown, the insulation times above 0°C are 6 hours for water-based A-10, over 12 hours for eutectic salt B-4, and 2 hours for commercial ice packs; the insulation times for 2-8°C are 5 hours, 10 hours, and 4 hours; the lowest temperatures are -19.5°C, -20.2°C, and -19.8°C, respectively; the temperature uniformity σ is 1.0-2.5°C, 0.5-1.0°C, and 2.5-4.5°C, respectively; the temperature fluctuation of eutectic salt B-4 is relatively stable, while the temperature fluctuations of water-based A-10 and commercial ice packs are relatively large.

[0107] Temperature distribution uniformity data such as Figure 6 As shown, the eutectic salt B-4 exhibits stable distribution uniformity, the smallest standard deviation, and a maximum temperature difference of only 0.8°C, while the water-based A-10 outperforms commercial ice packs.

[0108] Overall assessment: The water-based system is suitable for e-commerce and same-city instant delivery of fresh fruits and vegetables in cold chain transportation; while the eutectic salt system is suitable for pharmaceutical cold chain such as vaccines and blood, international cold chain transportation, and deep-frozen products.

[0109] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0110] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A manufacturing process for an insulated box for cold chain logistics, characterized in that: Includes the following steps: S1, Preparation of phase change cold storage materials (1) Expanded graphite was pressed into a material with a density of 0.1 g / cm³. 3 Construct a three-dimensional thermally conductive framework from the bulk material: The preparation of modified expanded graphite includes the following steps: For pretreatment, polyvinylpyrrolidone (PVP) was dissolved in deionized water, and expanded graphite (EG) was added. The mass ratio of EG to PVP was 3:

1. The mixture was stirred at 600 r / min for 1 h at room temperature. After filtration and washing, it was dried at 80°C for 12 h to obtain pretreated expanded graphite. In-situ growth was performed by adding pretreated expanded graphite and tetraethyl orthosilicate to anhydrous ethanol at a mass-to-volume ratio of 6 g:35 mL, ultrasonicating for 5 min, transferring to a 40°C water bath, adding 30 wt% ammonia solution while stirring at 300 r / min, reacting for 6 h, filtering and washing, and drying at 60°C for 12 h to obtain SiO2-modified expanded graphite, wherein the mass loading of SiO2 was 7 wt%. (2) Preparation of precursor solution: Sodium acrylate monomer, crosslinking agent N,N'-methylenebisacrylamide and initiator ammonium persulfate are dissolved in deionized water, wherein the concentration of sodium acrylate is 15wt%, the mass ratio of crosslinking agent to sodium acrylate is 1:15, and the mass ratio of initiator to sodium acrylate is 1:

4. (3) The modified expanded graphite block was placed in the precursor solution and immersed for 2 hours under an absolute pressure of 0.1-0.2 atm; (4) The impregnated block was transferred to a 50°C hot air chamber for in-situ polymerization reaction for 10 h to obtain a modified expanded graphite-sodium polyacrylate dual network carrier. (5) Secondary water absorption process: the phase change material is deionized water. The modified expanded graphite-sodium polyacrylate double network carrier is soaked in deionized water for 12 hours. H2O is loaded into the expanded graphite-sodium polyacrylate double network and the mass fraction of H2O is 80% to obtain a shaped composite phase change cold storage material. S2, Cold Storage Box Assembly The outer and inner boxes are made of foamed polypropylene material. The inner wall of the inner box is grooved around the perimeter. The shaped composite phase change cold storage material prepared in step S1 is cut into suitable cold storage sheets. After the cold storage sheets are pre-cooled, an aluminum-plastic composite film is wrapped around the surface of the cold storage sheets. Thermally conductive silicone pads are attached to the grooves. The cold storage sheets and the inner box form a tight thermal contact through the thermally conductive silicone pads. The outer and inner boxes are assembled to obtain the cold chain logistics insulated box.

2. The manufacturing process of a cold chain logistics insulated box according to claim 1, characterized in that: In S1, (5) secondary water absorption is replaced by vacuum impregnation melt blending method. The phase change material and the modified expanded graphite-sodium polyacrylate dual network carrier are mixed at a mass ratio of 80:20, heated until the phase change material melts, impregnated under a vacuum of 0.08MPa for 20min, with stirring during the process, and then cooled and shaped to obtain a shaped composite phase change cold storage material. The phase change material is a ternary eutectic salt of Na2SO4·10H2O-MgSO4·7H2O-water, and its preparation includes the following steps: Na2SO4·10H2O, MgSO4·7H2O and deionized water (H2O) were mixed in a mass ratio of 1:4:5 and heated to complete melting under magnetic stirring at a speed of 300 r / min until the solution became clear and transparent, thus obtaining the phase change material.

3. The manufacturing process of a cold chain logistics insulated box according to claim 2, characterized in that: In S1, the particle size of expanded graphite is 100 mesh.

4. A cold chain logistics insulated box, characterized in that: The cold chain logistics insulated box is manufactured by the cold chain logistics insulated box manufacturing process described in any one of claims 1-3. The cold chain logistics insulated box includes an outer box, an inner box, and a cold storage sheet. The cold storage sheet is a double-network shaped composite phase change cold storage material. The phase change material is loaded in the pores of the double-network carrier. The cold storage sheet is detachably disposed in the slots around the inner wall of the inner box.

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