Supercritical CO2-based foaming device and method thereof

Abstract

The invention relates to the technical field of foaming devices, in particular to a foaming device based on supercritical CO2 and a method thereof. According to the technical scheme, the device comprises a reaction kettle, a carbon dioxide conveying part, a negative pressure part, a shielding gas part, a circulating part, a temperature control part and a supporting plate system arranged in the kettle. The supporting plate system is provided with an accommodating chamber with an arc-shaped bottom surface, normal micropores are formed in the bottom, and a polymer sample can be suspended through airflow and is prevented from being in contact with a supporting surface, so that full-surface uniform foaming is realized. The method comprises the steps of loading, atmosphere replacement, supercritical environment establishment, dissolution saturation, rapid pressure relief foaming, unloading and the like. The method can effectively eliminate the shadow effect, improves the foaming uniformity and the product performance consistency, and is suitable for microcellular foaming preparation of various polymer materials.

Description

Technical Field

[0001] This invention relates to the field of foaming device technology, and more particularly to a foaming device and method based on supercritical CO2. Background Technology

[0002] The supercritical CO2-based foaming device is an advanced process equipment for preparing microporous polymer materials by utilizing the unique properties of supercritical fluids. Its core working principle lies in leveraging the combined high diffusivity of supercritical CO2 (gas) and strong solubility of liquid. Under specific temperature and pressure conditions, CO2 in a supercritical state fully permeates and dissolves into the polymer matrix. Subsequently, by triggering rapid pressure release, the system undergoes a sharp thermodynamic instability, causing the dissolved CO2 to rapidly supersaturate and homogeneously nucleate within the polymer, growing and forming numerous micron- or nano-scale closed or interconnected pores, thereby obtaining a foamed material with a controllable pore structure. The entire process is green and environmentally friendly, leaving no solvent residue, providing a key technological means for the lightweighting and functionalization of polymer materials.

[0003] The engineering implementation of existing devices still faces several key technical bottlenecks, restricting their application in the preparation of highly uniform and high-performance products. One prominent problem is the inherent defects of traditional sample support methods. Currently, mesh or flat support frames are typically used within the devices to hold polymer samples, such as preforms or microspheres. This support method physically blocks the contact area between the sample and the support, hindering the uniform penetration and diffusion of supercritical CO2 fluid, creating a so-called shadowing effect in this contact area. As a result, the polymer in the blocked area foams insufficiently or not at all, creating a significant difference in pore size and density compared to the non-contact area, leading to a non-uniform structure and dispersed performance in the final product. This non-uniformity severely affects the reliability and repeatability of material properties; for example, in the preparation of porous microspheres for adsorption separation, it directly leads to a decrease in their adsorption capacity and efficiency. Summary of the Invention

[0004] The purpose of this invention is to address the problem in the prior art that polymer samples cannot be uniformly exposed on the entire surface during supercritical treatment, thus failing to eliminate the shadowing effect, and to propose a supercritical CO2 foaming device and method.

[0005] On the one hand, this application proposes a supercritical CO2 foaming device, including a reactor and a carbon dioxide conveying component connected to the reactor for introducing supercritical carbon dioxide into the reactor, a negative pressure component for evacuating the reactor, a protective gas component for introducing inert gas into the reactor, a circulation component for driving the supercritical carbon dioxide to circulate in the reactor, and a temperature control component for heating the reactor.

[0006] A support plate system installed inside the reactor to support polymers includes a connecting plate fixedly installed inside the reactor and a support plate detachably installed on the connecting plate. The support plate is provided with multiple receiving chambers for supporting polymers. The bottom of each receiving chamber is provided with an arc-shaped bottom surface. Multiple micropores are arranged in a circular array on the arc-shaped bottom surface. The axial direction of the micropores is perpendicular to the tangential direction of the arc-shaped bottom surface.

[0007] Optionally, the connecting plate is provided with an air blowing chamber, the connecting plate is provided with a protruding positioning ring and a positioning pin, the support plate is provided with a connecting lug that connects to the positioning pin, the connecting plate and the support plate are fixedly connected by a nut, and a sealing ring that cooperates with the positioning ring is fixedly installed on the support plate.

[0008] The receiving chamber includes a tapered tube that gradually tapers from top to bottom, and a connector is provided at the bottom of the tapered tube, on which an air blowing head is detachably installed.

[0009] Optionally, the air blower head includes an outer steel mesh threaded to the connector head and an inner steel mesh located inside the outer steel mesh. An elastic soft pad is fixedly installed between the outer steel mesh and the inner steel mesh. The microholes are located on the soft pad. The outer steel mesh is provided with a threaded line that is threaded to the connector head.

[0010] Optionally, a tensioning structure is provided on the soft pad and on one side of the micropores. The tensioning structure includes an air chamber on the soft pad. Both ends of the air chamber are provided with outwardly expanding conical expansion holes. A sealing plate for sealing the air chamber is fixedly installed in the conical expansion holes. The air chamber is filled with high-pressure gas.

[0011] Optionally, the carbon dioxide delivery component includes a carbon dioxide storage tank, a refrigerator, and a first high-pressure plunger pump installed on one side of the reactor. The carbon dioxide storage tank is connected to the refrigerator via a first gas delivery pipe. The refrigerator is connected to the input end of the first high-pressure plunger pump via a second gas delivery pipe. The output end of the first high-pressure plunger pump is connected to the interior of the reactor via a third gas delivery pipe.

[0012] Optionally, the negative pressure component includes a vacuum pump installed on one side of the reactor, the vacuum pump being connected to the reactor via a suction pipe.

[0013] Optionally, the protective gas component includes an inert gas storage tank and a second high-pressure plunger pump fixedly installed on one side of the reactor. The inert gas storage tank and the input end of the second high-pressure plunger pump are connected through a first transmission pipe, and the output end of the second high-pressure plunger pump is connected to the interior of the reactor through a second transmission pipe.

[0014] Optionally, the circulation component includes a third high-pressure plunger pump fixedly installed on the reactor. The input end of the third high-pressure plunger pump is connected to the inside of the reactor through a first circulation pipe. A second circulation pipe is fixedly installed on the output end of the third high-pressure plunger pump. A three-way valve is fixedly installed on the second circulation pipe. The third circulation pipe is connected to the three-way valve. The other end of the third circulation pipe is connected to the bottom of the reactor.

[0015] The circulation component also includes a branch pipeline for inputting supercritical carbon dioxide into the gas blowing chamber. The branch pipeline includes a mass flow controller fixedly installed on a three-way valve. A first branch pipe is connected to the mass flow controller. A second branch pipe connected to the gas blowing chamber is fixedly installed inside the reactor. The first branch pipe and the second branch pipe are connected.

[0016] Optionally, the temperature control component includes a sealing cover fixedly installed on the outside of the reactor, forming a heating chamber between the sealing cover and the outer wall of the reactor. A water tank and a circulating pump are installed on one side of the reactor. The water tank is equipped with a heating wire and a temperature monitor. One end of the water tank is connected to the heating chamber through a first heat-conducting pipe, and the other end of the water tank is connected to the input end of the circulating pump through a second heat-conducting pipe. The output end of the circulating pump is connected to the heating chamber through a third heat-conducting pipe.

[0017] A sealing door is detachably installed on the reactor and the sealing cover, and the sealing door seals both the reactor and the sealing cover.

[0018] On the other hand, this application proposes a supercritical CO2 foaming method, applied to the supercritical CO2 foaming device described above. This method includes the following steps:

[0019] Step 1: Place the polymer sample into the receiving chamber of the support plate, install the support plate system, and close the sealing door;

[0020] First, start the vacuum pump to evacuate the reactor, then use the second high-pressure plunger pump to fill the reactor with inert gas, repeating this process several times to remove oxygen and moisture.

[0021] Step 2: Start the carbon dioxide delivery unit. After the liquid CO2 is cooled by the refrigerator, it is pressurized and delivered to the reactor by the first high-pressure plunger pump. At the same time, the temperature control unit heats the inside of the reactor to make the CO2 reach the supercritical state.

[0022] Step 3: Start the third high-pressure plunger pump in the circulation component to drive the supercritical CO2 to circulate in the reactor. At the same time, supply gas to the gas blowing chamber through the branch pipeline so that the polymer sample is suspended in the containment chamber and uniformly adsorbs CO2.

[0023] Step 4: After saturation, quickly reduce the pressure inside the reactor using a negative pressure component or a dedicated pressure relief valve to allow the dissolved CO2 to precipitate rapidly and form uniform micropores inside the polymer.

[0024] Step 5: After foaming is complete, restore normal pressure, open the sealed door, remove the support plate and the foamed product, and carry out subsequent processing or testing.

[0025] Compared with the prior art, this application includes at least one of the following beneficial technical effects:

[0026] By designing a tray system with an arc-shaped bottom surface and a normal microporous structure, and combining it with an airflow suspension mechanism, the problem of uneven foaming in the polymer contact area caused by traditional support methods is fundamentally solved. This device can achieve non-contact support and uniform exposure of the entire surface of polymer samples, significantly improving the uniformity of the foaming structure and the consistency of product performance.

[0027] The system integrates functional modules such as carbon dioxide delivery, atmosphere control, fluid circulation and temperature control, realizing full-process automation and precise control of supercritical foaming process. It has the advantages of simple operation, strong process adaptability and convenient maintenance, and is suitable for the preparation of high-performance microporous polymer materials. Attached Figure Description

[0028] Figure 1 Schematic diagram of the foaming device Figure 1 ;

[0029] Figure 2 Schematic diagram of the foaming device Figure 2 ;

[0030] Figure 3 Schematic diagram of the foaming device Figure 3 ;

[0031] Figure 4 This is a schematic diagram of the reactor structure;

[0032] Figure 5 This is a schematic diagram of the flow of the heat-conducting medium;

[0033] Figure 6 This is a schematic diagram of the internal structure of the reactor;

[0034] Figure 7 Schematic diagram of the pallet system Figure 1 ;

[0035] Figure 8 Schematic diagram of the pallet system Figure 2 ;

[0036] Figure 9 Schematic diagram of the pallet system Figure 3 ;

[0037] Figure 10 A schematic diagram of the containment chamber and the air nozzle;

[0038] Figure 11 This is a schematic diagram of the air blower's structure;

[0039] Figure 12 This is a schematic diagram of the tension structure and the micropores.

[0040] Attached reference numerals: 1. Reactor; 11. Sealed door;

[0041] 2. Carbon dioxide conveying components; 21. Carbon dioxide storage tank; 22. Refrigeration unit; 23. First high-pressure plunger pump; 24. First gas delivery pipe; 25. Second gas delivery pipe; 26. Third gas delivery pipe;

[0042] 3. Negative pressure components; 31. Vacuum pump; 32. Suction tube;

[0043] 4. Protective gas components; 41. Inert gas storage tank; 42. Second high-pressure plunger pump; 43. First transmission pipe; 44. Second transmission pipe;

[0044] 5. Circulation components; 51. Third high-pressure plunger pump; 52. First circulation pipe; 53. Second circulation pipe; 54. Three-way valve; 55. Third circulation pipe;

[0045] 6. Temperature control component; 61. Sealing cover; 62. Heating chamber; 63. Water tank; 64. Circulation pump; 65. First heat pipe; 66. Second heat pipe; 67. Third heat pipe;

[0046] 7. Support plate system; 71. Connecting plate; 711. Air blowing chamber; 712. Positioning ring; 713. Positioning pin; 72. Support plate; 721. Connecting lug; 722. Nut; 723. Sealing ring; 73. Receiving chamber; 731. Tapered tube; 732. Connector; 74. Air blowing head; 741. Inner steel mesh; 742. Outer steel mesh; 743. Soft pad; 744. Threaded wire; 75. Tensioning structure; 751. Micropore; 752. Air chamber; 753. Tapered expansion hole; 754. Sealing plate;

[0047] 8. Branch pipe; 81. Mass flow controller; 82. First branch pipe; 83. Second branch pipe. Detailed Implementation

[0048] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0049] Example: Figures 1 to 6 As shown, the supercritical CO2 foaming device proposed in this application includes a reactor 1 and a carbon dioxide conveying component 2 connected to the reactor 1 for introducing supercritical carbon dioxide into the reactor, a negative pressure component 3 for evacuating the reactor 1, a protective gas component 4 for introducing inert gas into the reactor 1, a circulation component 5 for driving the supercritical carbon dioxide to circulate in the reactor 1, and a temperature control component 6 for heating the reactor 1. Through the coordinated operation of the above components, a complete supercritical foaming process system is formed.

[0050] The carbon dioxide delivery component 2 is used to establish and maintain a high-pressure supercritical environment inside the reactor, serving as the source of the foaming medium. The negative pressure component 3, used in conjunction with the protective gas component 4, is used to replace the air inside the reactor after feeding, aiming to completely remove oxygen and moisture. Its purpose is to prevent the polymer from oxidizing and degrading under high temperature and pressure, and to eliminate the possible inhibitory effect of oxygen on subsequent processes, ensuring process safety and product quality. The circulation component 5 is used to drive the forced flow of supercritical CO2 inside the reactor to eliminate temperature and concentration gradients, ensuring uniform saturation of all parts of the polymer. This is crucial for obtaining a foamed structure with a consistent pore size distribution. The temperature control component 6 provides precise temperature control for the entire reaction process, because the solubility of supercritical CO2 and the viscoelasticity of the polymer are extremely sensitive to temperature. Precise temperature control is the key to controlling the cell morphology.

[0051] Specifically, the usage process is as follows: after loading, the air is first replaced by the negative pressure component 3 and the protective gas component 4, then the pressure and temperature are increased to the supercritical state by the carbon dioxide conveying component 2 and the temperature control component 6, then the circulation component 5 is started to saturate for a predetermined time, and finally the negative pressure component 3 or the independent pressure relief valve realizes rapid pressure relief foaming.

[0052] like Figures 1 to 6In this embodiment, the carbon dioxide delivery component 2 includes a carbon dioxide storage tank 21, a refrigerator 22, and a first high-pressure plunger pump 23 installed on one side of the reactor 1. The carbon dioxide storage tank 21 is connected to the refrigerator 22 through a first gas delivery pipe 24. The refrigerator 22 is connected to the input end of the first high-pressure plunger pump 23 through a second gas delivery pipe 25. The output end of the first high-pressure plunger pump 23 is connected to the inside of the reactor 1 through a third gas delivery pipe 26. Liquid CO2 flows out from the carbon dioxide storage tank 21 and is kept in a low-temperature liquid state by the refrigerator 22 to prevent it from vaporizing before entering the first high-pressure plunger pump 23. The first high-pressure plunger pump 23 pressurizes the liquid CO2 to a pressure much higher than the critical pressure. After the high-pressure liquid CO2 flows through the preheating pipeline or enters the reactor 1, it absorbs heat and reaches the supercritical temperature, thereby transforming into a supercritical fluid.

[0053] The refrigeration unit 22 ensures that the input end of the first high-pressure plunger pump 23 is a pure liquid phase, thereby improving the volumetric efficiency and operational stability of the first high-pressure plunger pump 23, which in turn provides a high-pressure source.

[0054] like Figures 1 to 6 In this embodiment, the negative pressure component 3 includes a vacuum pump 31 installed on one side of the reactor 1. The vacuum pump 31 is connected to the reactor 1 through a suction pipe 32. After feeding and sealing the reactor 1, the vacuum pump 31 is started to extract the gas in the reactor 1 through the suction pipe 32, reducing the pressure to far below atmospheric pressure. This can initially remove most of the air in the reactor 1, creating favorable conditions for the subsequent introduction of inert protective gas.

[0055] Furthermore, the protective gas component 4 includes an inert gas storage tank 41 and a second high-pressure plunger pump 42 fixedly installed on one side of the reactor 1. The inert gas storage tank 41 and the input end of the second high-pressure plunger pump 42 are connected through a first transmission pipe 43. The output end of the second high-pressure plunger pump 42 is connected to the interior of the reactor 1 through a second transmission pipe 44. The second high-pressure plunger pump 42 pressurizes the gas in the inert gas storage tank 41, such as high-purity nitrogen, and injects it into the reactor 1. When used in conjunction with the negative pressure component 3, it can perform a vacuuming-inert gas filling cycle operation and perform the cycle 2-3 times.

[0056] The specific process is as follows: first, the negative pressure component 3 draws a vacuum, and then the protective gas component 4 injects inert gas to a slightly positive pressure. This process is repeated. This cycle can efficiently reduce the oxygen and moisture concentration in the reactor 1 to an extremely low level, forming a pure inert atmosphere, which can ensure that the subsequent supercritical foaming process is free from oxidation interference and that the product performance is stable.

[0057] like Figures 1 to 6In this embodiment, the circulation component 5 includes a third high-pressure plunger pump 51 fixedly installed on the reactor 1. The input end of the third high-pressure plunger pump 51 is connected to the inside of the reactor 1 through a first circulation pipe 52. The output end of the third high-pressure plunger pump 51 is fixedly installed with a second circulation pipe 53. A three-way valve 54 is fixedly installed on the second circulation pipe 53. A third circulation pipe 55 is connected to the three-way valve 54. The other end of the third circulation pipe 55 is connected to the bottom of the reactor 1. When the third high-pressure plunger pump 51 is started, the supercritical CO2 fluid in the upper part of the reactor is drawn out through the first circulation pipe 52, pressurized, and then transported through the second circulation pipe 53. By adjusting the three-way valve 54, the fluid can return to the bottom of the reactor through the third circulation pipe 55.

[0058] A forced convection circulation from top to bottom can be formed in reactor 1, which significantly enhances the mass and heat transfer process of the fluid in reactor 1, making the temperature and CO2 concentration distribution quickly and uniform, avoiding local concentration unevenness caused by static saturation, thus ensuring that all polymer samples and even different parts of the samples can complete the dissolution and saturation of CO2 under the same conditions.

[0059] like Figures 1 to 6 In this embodiment, the temperature control component 6 includes a sealing cover 61 fixedly installed on the outside of the reactor 1. A heating chamber 62 is formed between the sealing cover 61 and the outer wall of the reactor 1. A water tank 63 and a circulation pump 64 are installed on one side of the reactor 1. The water tank 63 is equipped with a heating wire and a temperature monitor. One end of the water tank 63 is connected to the heating chamber 62 through a first heat conduction pipe 65, and the other end of the water tank 63 is connected to the input end of the circulation pump 64 through a second heat conduction pipe 66. The output end of the circulation pump 64 is connected to the heating chamber 62 through a third heat conduction pipe 67. When the circulation pump 64 is started, the heat conduction medium in the water tank 63 is driven. The heat conduction medium can be either silicone oil or water. The heat conduction medium flows through the heating chamber 62 to form a closed loop.

[0060] The heating wire in the water tank 63 heats according to the feedback from the temperature monitor, keeping the heat transfer medium at a constant temperature. The heat is evenly transferred to the internal material through the wall of the reactor 1, which can achieve uniform and precise programmed temperature control of the entire reactor 1, and can quickly respond to the heating, heat preservation and cooling steps required by the process.

[0061] The reactor 1 and the sealing cover 61 are detachably equipped with sealing doors 11. The sealing doors 11 seal both the reactor 1 and the sealing cover 61. Opening the sealing doors 11 facilitates the placement or removal of polymer samples and the support plate system 7 inside the reactor 1. Closing and locking the sealing doors 11 can simultaneously isolate and seal the high-pressure chamber of the reactor 1 and the heating chamber 62 of the sealing cover 61, effectively preventing the heat transfer medium in the heating chamber 62 from leaking into the reactor 1 and contaminating the material. It also prevents the high-pressure medium inside the reactor from leaking out, ensuring the safety of the equipment and the cleanliness of the process.

[0062] like Figures 5 to 12 As shown, this embodiment also includes a support plate system 7 installed inside the reactor 1 to support the polymer. The support plate system 7 includes a connecting plate 71 fixedly installed inside the reactor 1 and a support plate 72 detachably installed on the connecting plate 71. The support plate 72 is provided with multiple receiving chambers 73 for supporting the polymer. The bottom of the receiving chamber 73 is provided with an arc-shaped bottom surface. Multiple microholes 751 are arranged in a circular array on the arc-shaped bottom surface. The axial direction of the microholes 751 is perpendicular to the tangent direction of the arc-shaped bottom surface. When the branch pipe 8 supplies air to the air blowing chamber 711, the gas is ejected from the arc-shaped bottom surface in the normal direction through the microholes 751. The setting of the microhole axis perpendicular to the tangent of the bottom surface makes the airflow uniformly directed from all parts of the groove sidewall toward the central axis of the receiving chamber. The ejected airflow can converge at the center of the receiving chamber to form a stable upward force to lift the polymer microspheres. At the same time, a horizontal component force is generated to push the microspheres toward the center, thereby effectively avoiding contact between the microspheres and the sidewall of the receiving chamber and fundamentally eliminating the contact shadow area caused by traditional flat plate support.

[0063] Compared to simply drilling vertical holes on a curved surface, this design uses normal openings to generate a clearly oriented flow field, ensuring uniform and concentrated levitation force. This avoids the drawbacks of vertical holes causing airflow divergence and mutual interference due to different positions, and is the key to achieving uniform and stable levitation of microspheres in the groove and contactless processing.

[0064] Furthermore, the connecting plate 71 is equipped with an air blowing chamber 711, and the connecting plate 71 is equipped with a raised positioning ring 712 and a positioning pin 713. The support plate 72 is equipped with a connecting ear 721 that connects to the positioning pin 713. The connecting plate 71 and the support plate 72 are fixedly connected by a nut 722. A sealing ring 723 that cooperates with the positioning ring 712 is fixedly installed on the support plate 72. When loading or unloading materials, loosening the nut 722 can separate the support plate 72 from the connecting plate 71, thereby removing the entire support plate 72 from the reactor 1. This greatly facilitates the batch loading and unloading of polymer microspheres and improves operating efficiency. The positioning pin 713 and the positioning ring 712 ensure the positional accuracy and repeatability of the support plate 72 each time it is installed. The tight cooperation between the sealing ring 723 and the positioning ring 712 ensures the high-pressure sealing of the air blowing chamber 711, preventing gas leakage from the connection and ensuring that all gas can be ejected from the designed micropores 751.

[0065] It is worth noting that the circulation component 5 also includes a branch pipe 8 for inputting supercritical carbon dioxide into the gas blowing chamber 711. The branch pipe 8 includes a mass flow controller 81 fixedly installed on the three-way valve 54. A first branch pipe 82 is connected to the mass flow controller 81. A second branch pipe 83 connected to the gas blowing chamber 711 is fixedly installed inside the reactor 1. The first branch pipe 82 and the second branch pipe 83 are connected.

[0066] The supercritical CO2 output by the third high-pressure plunger pump 51 in the circulation component 5 is partially diverted by the three-way valve 54 and enters the branch pipe 8. The airflow is first precisely measured and regulated by the mass flow controller 81, and then passes through the first branch pipe 82 and the second branch pipe 83 in sequence, and finally enters the air blowing chamber 711 of the connecting plate 71, and is ejected from the micropores 751 of the support plate 72. The mass flow controller 81 ensures that the airflow supplied to the suspension air cushion is constant and is not affected by the pressure fluctuation of the main circuit, thus maintaining the stable suspension height of the microspheres.

[0067] The containment chamber 73 includes a tapered tube 731 that gradually tapers from top to bottom. A connector 732 is located below the tapered tube 731, and an air blowing head 74 is detachably installed on the connector 732. The design of the tapered tube 731 allows the polymer microspheres to naturally concentrate in the air blowing head 74 area at the bottom under the action of gravity, while preventing the microspheres from escaping from the top during suspension or transportation. The air blowing head 74 is detachably installed on the connector 732, which facilitates the individual replacement and maintenance of easily worn or clogged microporous structural components, reduces the overall cost, and provides flexibility for future replacement of air blowing heads 74 with different micropore parameters according to different polymer microsphere characteristics, such as size and density, thereby enhancing the process adaptability of the equipment.

[0068] Furthermore, the air blower head 74 includes an outer steel mesh 742 threadedly connected to the connector 732 and an inner steel mesh 741 located inside the outer steel mesh 742. An elastic soft pad 743 is fixedly installed between the outer steel mesh 742 and the inner steel mesh 741. Microholes 751 are located on the soft pad 743. The outer steel mesh 742 has threaded lines 744 that are threadedly connected to the connector 732. The inner steel mesh 741 and the outer steel mesh 742 act as a rigid frame, providing support for the soft pad 743 and maintaining its curved contour. 743 can be made of special elastic material that is resistant to high temperature and supercritical fluid. It is easy to perform precision micro-hole processing in its undeformed state. After processing, the flat soft pad 743 is bent and clamped and fixed between the inner and outer steel meshes, so that it is deformed into the required arc shape. At this time, the direction of the micro-hole 751 also changes to the normal direction along the deformed curved surface. This cleverly solves the manufacturing problem of directly processing normal micro-holes on complex three-dimensional curved surfaces. The threaded connection of the outer steel mesh 742 facilitates the installation and sealing of the overall air blower.

[0069] It should be noted that this structure based on the pad 743 also has potential drawbacks: after the elastic material is processed in the micropores 751, the micropores 751 may shrink or even partially close due to their own internal stress rebound, making the micropores 751 unusable.

[0070] like Figure 12As shown, in this embodiment, a tensioning structure 75 is provided on the soft pad 743 and located on one side of the micropore 751. The tensioning structure 75 includes an air chamber 752 provided on the soft pad 743. Both ends of the air chamber 752 are provided with outwardly expanding conical expansion holes 753. A sealing piece 754 for sealing the air chamber 752 is fixedly installed in the conical expansion holes 753. The air chamber 752 is filled with high-pressure gas. The tensioning structure 75 is designed to overcome the above-mentioned disadvantages. The design of the tensioning structure 75 provides a micropore opening and closing mechanism that is adaptive to environmental pressure, effectively overcoming the disadvantage that the micropores of the soft pad are prone to failure due to contamination or material rebound.

[0071] In the non-working state, such as when reactor 1 is opened for material handling, the interior of reactor 1 is at atmospheric pressure. At this time, the high-pressure gas pre-filled in the gas chamber 752 causes its inner wall to expand outward. This expansion force is transmitted to the adjacent micropore 751 area, causing the walls of the micropore 751 to fit tightly or even close, thus forming a physical seal and effectively preventing external contaminants from entering the micropores and causing blockage. When the reactor 1 is pressurized to the supercritical working pressure, the external environmental pressure is higher than the internal pressure of the gas chamber 752. Under this pressure difference, the sealing piece 754 is recessed inward to the inside of the gas chamber 752. The inward movement of the sealing piece 754, through its connection point with the soft pad 743, generates a radial inward pulling force on the surrounding soft pad 743 material, causing the soft pad 743 to shrink and deform locally. This shrinkage first creates a tiny opening at the port of the micropore 751. As the external high-pressure fluid enters through this tiny opening, the pressure is further transmitted, eventually causing the micropore 751 to fully open and restore the designed flow state.

[0072] The micropore 751 achieves pressure-driven self-opening and closing, automatically sealing and preventing contamination during storage and loading / unloading, and automatically and reliably opening during the process stage, greatly improving the system's reliability and ease of maintenance.

[0073] On the other hand, this application proposes a supercritical CO2-based foaming method, applied to the above-mentioned supercritical CO2-based foaming device, which includes the following steps:

[0074] Step 1: Place the polymer sample into the receiving chamber 73 of the support plate 72, install the support plate system 7 and close the sealing door 11;

[0075] First, start the vacuum pump 31 to evacuate the reactor 1, then use the second high-pressure plunger pump 42 to fill the reactor with inert gas, repeating this process several times to remove oxygen and moisture.

[0076] Step 2: Start the carbon dioxide delivery component 2, cool the liquid CO2 through the refrigerator 22, and then pressurize and deliver it to the reaction vessel 1 by the first high-pressure plunger pump 23. At the same time, the temperature control component 6 heats the inside of the vessel to make the CO2 reach the supercritical state.

[0077] Step 3: Start the third high-pressure plunger pump 51 in the circulation component 5 to drive the supercritical CO2 to circulate in the reactor. At the same time, supply gas to the gas blowing chamber 711 through the branch pipeline 8 so that the polymer sample is suspended in the containment chamber and uniformly adsorbs CO2.

[0078] Step 4: After saturation, quickly reduce the pressure inside the reactor using negative pressure component 3 or a dedicated pressure relief valve to allow the dissolved CO2 to precipitate rapidly and form uniform micropores inside the polymer.

[0079] Step 5: After foaming is complete, restore normal pressure, open the sealed door 11, take out the support plate 72 and the foamed finished product, and carry out subsequent processing or testing.

[0080] In this embodiment, the reactor 1 is equipped with a tray system 7 that can support polymer samples. The bottom of the receiving chamber 73 is arc-shaped and has normal micropores 751. During the process, the carbon dioxide conveying component 2 cools the liquid CO2 through the refrigerator 22, pressurizes it by the first high-pressure plunger pump 23 and inputs it into the reactor 1. Under the heating of the temperature control component 6, it is converted into a supercritical state. The negative pressure component 3 and the protective gas component 4 first evacuate the reactor and replace it with inert gas to remove oxygen and moisture. The circulation component 5 drives the supercritical CO2 to circulate in the reactor through the third high-pressure plunger pump 51 to ensure uniform fluid distribution. At the same time, the branch pipeline 8 delivers a portion of the supercritical CO2 to the air blowing chamber 711 of the connecting plate 71 after being regulated by the mass flow controller 81. Then, it is sprayed upward through the micropores 751, so that the polymer microspheres are suspended in the receiving chamber, avoiding contact with the wall surface, thereby eliminating the shadow effect and achieving uniform foaming of the entire surface.

[0081] The above specific embodiments are merely several optional embodiments of the present invention. Based on the technical solutions of the present invention and the relevant teachings of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.

Claims

1. A supercritical CO2 foaming device, characterized in that, include: The reactor (1) and the carbon dioxide conveying component (2) connected to the reactor (1) for introducing supercritical carbon dioxide into the reactor, the negative pressure component (3) for evacuating the reactor (1), the protective gas component (4) for introducing inert gas into the reactor (1), the circulation component (5) for driving the supercritical carbon dioxide to circulate in the reactor (1), and the temperature control component (6) for heating the reactor (1). The pallet system (7) installed inside the reactor (1) to support the polymer includes a connecting plate (71) fixedly installed inside the reactor (1) and a support plate (72) detachably installed on the connecting plate (71). The support plate (72) is provided with a plurality of receiving chambers (73) for supporting the polymer. The bottom of the receiving chamber (73) is provided with an arc-shaped bottom surface. A plurality of microholes (751) are arranged in a circular array on the arc-shaped bottom surface. The axial direction of the microholes (751) is perpendicular to the tangential direction of the arc-shaped bottom surface.

2. The supercritical CO2-based foaming device according to claim 1, characterized in that, The connecting plate (71) is provided with an air blowing chamber (711), the connecting plate (71) is provided with a protruding positioning ring (712) and a positioning pin (713), the support plate (72) is provided with a connecting ear (721) connected to the positioning pin (713), the connecting plate (71) and the support plate (72) are fixedly connected by a nut (722), and a sealing ring (723) that cooperates with the positioning ring (712) is fixedly installed on the support plate (72). The receiving chamber (73) includes a tapered tube (731) that gradually tapers from top to bottom, and a connector (732) is provided below the tapered tube (731). An air blower (74) is detachably installed on the connector (732).

3. The supercritical CO2-based foaming device according to claim 2, characterized in that, The air blower (74) includes an outer steel mesh (742) threaded onto a connector (732) and an inner steel mesh (741) located inside the outer steel mesh (742). An elastic soft pad (743) is fixedly installed between the outer steel mesh (742) and the inner steel mesh (741). The microhole (751) is located on the soft pad (743). The outer steel mesh (742) is provided with a threaded line (744) that is threadedly connected to the connector (732).

4. The supercritical CO2-based foaming device according to claim 3, characterized in that, A tensioning structure (75) is provided on the soft pad (743) and on one side of the micropore (751). The tensioning structure (75) includes an air chamber (752) on the soft pad (743). Both ends of the air chamber (752) are provided with outwardly expanding conical expansion holes (753). A sealing plate (754) for sealing the air chamber (752) is fixedly installed in the conical expansion hole (753). The air chamber (752) is filled with high-pressure gas.

5. The supercritical CO2-based foaming device according to claim 4, characterized in that, The carbon dioxide delivery component (2) includes a carbon dioxide storage tank (21), a refrigerator (22) and a first high-pressure plunger pump (23) installed on one side of the reactor (1). The carbon dioxide storage tank (21) is connected to the refrigerator (22) through a first gas delivery pipe (24). The refrigerator (22) is connected to the input end of the first high-pressure plunger pump (23) through a second gas delivery pipe (25). The output end of the first high-pressure plunger pump (23) is connected to the inside of the reactor (1) through a third gas delivery pipe (26).

6. The supercritical CO2-based foaming device according to claim 5, characterized in that, The negative pressure component (3) includes a vacuum pump (31) installed on one side of the reactor (1), and the vacuum pump (31) is connected to the reactor (1) through a suction pipe (32).

7. The supercritical CO2-based foaming device according to claim 6, characterized in that, The protective gas component (4) includes an inert gas storage tank (41) and a second high-pressure plunger pump (42) fixedly installed on one side of the reactor (1). The inert gas storage tank (41) and the input end of the second high-pressure plunger pump (42) are connected through a first transmission pipe (43). The output end of the second high-pressure plunger pump (42) is connected to the interior of the reactor (1) through a second transmission pipe (44).

8. The supercritical CO2-based foaming device according to claim 7, characterized in that, The circulation component (5) includes a third high-pressure plunger pump (51) fixedly installed on the reactor (1). The input end of the third high-pressure plunger pump (51) is connected to the inside of the reactor (1) through a first circulation pipe (52). The output end of the third high-pressure plunger pump (51) is fixedly installed with a second circulation pipe (53). A three-way valve (54) is fixedly installed on the second circulation pipe (53). A third circulation pipe (55) is connected to the three-way valve (54). The other end of the third circulation pipe (55) is connected to the bottom of the reactor (1). The circulation component (5) also includes a branch pipe (8) for inputting supercritical carbon dioxide into the gas blowing chamber (711). The branch pipe (8) includes a mass flow controller (81) fixedly installed on a three-way valve (54). A first branch pipe (82) is connected to the mass flow controller (81). A second branch pipe (83) connected to the gas blowing chamber (711) is fixedly installed inside the reactor (1). The first branch pipe (82) and the second branch pipe (83) are connected.

9. The supercritical CO2-based foaming device according to claim 8, characterized in that, The temperature control component (6) includes a sealing cover (61) fixedly installed on the outside of the reactor (1). A heating chamber (62) is formed between the sealing cover (61) and the outer wall of the reactor (1). A water tank (63) and a circulating pump (64) are installed on one side of the reactor (1). A heating wire and a temperature monitor are provided in the water tank (63). One end of the water tank (63) is connected to the heating chamber (62) through a first heat pipe (65). The other end of the water tank (63) is connected to the input end of the circulating pump (64) through a second heat pipe (66). The output end of the circulating pump (64) is connected to the heating chamber (62) through a third heat pipe (67). A sealing door (11) is detachably installed on the reactor (1) and the sealing cover (61), and the sealing door (11) seals both the reactor (1) and the sealing cover (61).

10. A supercritical CO2-based foaming method, applied to the supercritical CO2-based foaming device as described in claim 9, characterized in that, The method includes the following steps: Step 1: Place the polymer sample into the receiving chamber (73) of the support plate (72), install the support plate system (7) and close the sealing door (11). First, start the vacuum pump (31) to evacuate the reactor (1), and then fill the reactor with inert gas through the second high-pressure plunger pump (42). Repeat this process several times to remove oxygen and moisture. Step 2: Start the carbon dioxide delivery component (2), cool the liquid CO2 through the refrigerator (22), and then pressurize and deliver it to the reactor (1) by the first high-pressure plunger pump (23). At the same time, the temperature control component (6) heats the inside of the reactor so that the CO2 reaches the supercritical state. Step 3: Start the third high-pressure plunger pump (51) in the circulation component (5) to drive the supercritical CO2 to circulate in the reactor. At the same time, supply gas to the gas blowing chamber (711) through the branch pipeline (8) so that the polymer sample is suspended in the containment chamber and CO2 is uniformly adsorbed. Step 4: After saturation, the pressure inside the reactor is quickly reduced by the negative pressure component (3) or a special pressure relief valve, so that the dissolved CO2 is quickly released and forms uniform micropores inside the polymer. Step 5: After foaming is completed, restore normal pressure, open the sealed door (11), take out the support plate (72) and the foamed finished product, and carry out subsequent processing or testing.

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