Supercritical foaming apparatus and whole-process pressure-maintaining supercritical foaming method

Abstract

The present invention relates to the field of polymer material processing. Disclosed are a supercritical foaming apparatus and a whole-process pressure-maintaining supercritical foaming method. In the technical solution, the apparatus comprises a lower mold assembly and an upper mold assembly, wherein after the upper mold assembly and the lower mold assembly are clamped, a mold forming cavity is formed; and a fluid storage cavity in communication with the mold forming cavity is further provided in the upper mold assembly. The beneficial effects of the present invention are as follows: a dual-cavity structure of a fluid storage cavity and a mold forming cavity is used, wherein the mold forming cavity is used for ensuring the shape of a formed product, and the fluid storage cavity is used for the post-treatment of a supercritical fluid; and the fluid storage cavity is sealed, and the pressure of the fluid storage cavity is used to maintain the pressure of the mold forming cavity, thereby reducing the energy consumption of a supercritical fluid pressurization apparatus.

Description

A supercritical foaming device and a supercritical foaming method with pressure maintained throughout the process. Technical Field

[0001] This invention relates to the field of polymer material processing, and in particular to a supercritical foaming device and a supercritical foaming method with pressure maintained throughout the process. Background Technology

[0002] The core of in-mold supercritical fluid processing of polymer materials is to maintain the ultra-high pressure capability of the mold cavity while ensuring that the supercritical fluid enters the material in the mold cavity uniformly as quickly as possible.

[0003] To maintain high pressure within the mold: Patent application 1 (Chinese invention patent with publication number CN109435134A, specifically disclosing a supercritical gas foaming mold) employs a rectangular sealing gasket installed between two molds, then presses the upper and lower molds together to achieve a high-pressure seal of 25-30 MPa. This structure relies entirely on the pressure between the sealing gasket and the upper and lower molds, placing high demands on the pressure of the molding machine. Patent application 2 (Chinese invention patent with publication number CN112318809A, specifically disclosing a sealing structure and foaming mold for a foaming mold) invents a wedge-tightening fixed sealing strip, while utilizing damping grooves set in the upper and lower molds to achieve a high-temperature, high-pressure sealed foaming mold.

[0004] Patent applications 1 and 2 propose using molds to shape products and subject them to high-temperature, high-pressure supercritical fluid treatment. However, they do not solve the efficiency problem of rapid supercritical fluid treatment. During the treatment process, supercritical fluid must be continuously introduced into the mold cavity to maintain the high pressure of the mold cavity, resulting in high energy consumption and low efficiency. In addition, these two applications only target the treatment of regular sheet structures and cannot solve the problem of supercritical fluid treatment of irregular polymers.

[0005] Patent application 3 (Chinese utility model patent with publication number CN219466793U, which specifically discloses a supercritical fluid sealing molding mold) adopts a circular mold and sealing structure, which overcomes the defect of uneven stress distribution under high pressure in rectangular structures. Moreover, the upper and lower molds adopt a double sealing strip design on the contact surface and side to ensure the sealing of the mold during the supercritical fluid treatment process. However, when the mold is used for supercritical fluid treatment, the fluid needs to enter the mold forming cavity from the four sides of the mold, which will result in an excessively long material processing process in the middle part of the mold forming cavity. At the same time, if the molded product and its structure need to be changed, the entire mold needs to be remade, which results in high manufacturing costs.

[0006] In summary, in addition to solving the mold sealing problem to achieve high-temperature and high-pressure treatment of materials, supercritical fluid processing molds also need to solve the problem of uniform and rapid entry of supercritical fluid into the material. At the same time, in order to solve the versatility of the mold, the replaceability of the mold needs to be considered to reduce the mold manufacturing cost. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a supercritical foaming device and a supercritical foaming method with pressure maintained throughout the process.

[0008] The technical solution includes a lower mold assembly and an upper mold assembly, which together form a mold forming cavity.

[0009] The upper mold assembly also includes a fluid storage cavity that communicates with the mold forming cavity.

[0010] Preferably, the upper mold assembly is provided with a plurality of through holes and a through groove for connecting the plurality of through holes, and the fluid storage cavity and the mold forming cavity are connected through the through groove and the through holes.

[0011] Preferably, the mold forming cavity consists of a detachable lower module and a detachable upper module.

[0012] Preferably, the lower mold assembly includes a lower mold base and a lower module detachably connected to the lower mold base, wherein the lower module has a mold forming cavity.

[0013] The upper mold assembly includes an upper mold base, an upper mold intermediate mold detachably disposed on the upper mold base, an upper module detachably disposed on the upper mold intermediate mold, and an upper mold forming surface disposed on the upper module;

[0014] The upper mold forming surface and the lower module mold forming cavity combine to form a closed forming space.

[0015] Preferably, a lower mold placement cavity is formed on the lower mold base, and the lower module is detachably disposed in the lower mold placement cavity;

[0016] The side wall of the lower mold placement cavity is provided with a number of lower mold fixing holes evenly distributed in the circumferential direction;

[0017] The lower module corresponds to the shape of the lower mold placement cavity. Several lower mold mounting holes corresponding to the lower mold fixing holes are arranged circumferentially on its side wall. Both the lower mold fixing holes and the lower mold mounting holes are half holes. The lower mold mounting holes on the lower module and the corresponding lower mold fixing holes form a complete stepped hole after being combined.

[0018] Preferably, a through hole is formed on the side wall of the upper mold base, and an air inlet pipe and an air outlet pipe are fixedly installed at both ends of the through hole;

[0019] A connecting pipe is fixedly installed in the middle of the top surface of the upper mold base, and the connecting pipe is connected to the through hole;

[0020] A cylindrical fluid storage cavity is formed at the bottom of the intermediate mold of the upper mold, and the fluid storage cavity is connected to the connecting pipe;

[0021] A through vent is provided in the middle of the upper mold intermediate mold, one end of which is connected to the fluid storage cavity and the other end is connected to the guide groove.

[0022] The upper module has a plurality of through holes and a through groove for connecting the plurality of through holes, and a one-way valve is provided in each of the through holes.

[0023] The fluid storage cavity and the mold forming cavity are connected through the vent hole, the guide groove and the guide hole.

[0024] Preferably, a cylindrical upper mold placement cavity is formed at the top of the upper mold intermediate mold, and an upper module is detachably disposed within the upper mold placement cavity;

[0025] The upper mold placement cavity is cylindrical, and several upper mold fixing holes are evenly distributed circumferentially on the side wall of the upper mold placement cavity;

[0026] The upper module is cylindrical, and its side wall is provided with several upper mold mounting holes corresponding to the upper mold fixing holes. Both the upper mold fixing holes and the upper mold mounting holes are half holes. The upper mold mounting holes on the upper module and the corresponding upper mold fixing holes are combined to form a complete stepped hole.

[0027] Preferably, the top surface of the lower mold base is further provided with a lower sealing groove with a stepped cross-sectional shape. The lower sealing groove is located outside the lower mold placement cavity. A lower sealing ring is placed in the lower sealing groove and is placed at the lower part of the lower sealing groove.

[0028] The top of the upper mold intermediate mold is provided with an annular step, which is located outside the upper mold placement cavity and corresponds to the upper part of the lower sealing groove.

[0029] An upper sealing groove is formed on the side of the upper mold intermediate mold opposite to the annular step, and an upper sealing ring is placed in the upper sealing groove.

[0030] Preferably, the upper mold intermediate mold located outside the upper sealing groove is provided with a plurality of threaded holes arranged in a circumferential array, and the upper mold base plate is provided with a plurality of countersunk holes arranged in a circumferential array. The upper mold base and the upper mold intermediate mold are fixedly connected by intermediate mold bolts that pass through the countersunk holes and threaded holes.

[0031] A supercritical foaming method with pressure maintained throughout the entire process, characterized by comprising the following steps:

[0032] S1. Place the polymer raw material to be foamed into the mold chamber and close the upper and lower molds;

[0033] S2. A fluid storage cavity communicating with the mold chamber is provided in the upper mold;

[0034] S3. Place the mold into a hot press molding machine for hot pressing and fill the storage cavity with supercritical fluid at a certain pressure.

[0035] S4. Maintain constant temperature and pressure;

[0036] S5. Release the supercritical fluid in the storage chamber;

[0037] S6. The hot press molding machine opens the mold, and the polymer instantly foams and expands, jumping out of the mold chamber.

[0038] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows:

[0039] 1) The system adopts a dual-cavity structure of a fluid storage cavity and a mold forming cavity. The mold forming cavity is used to ensure the shape of the molded product, while the fluid storage cavity is used for post-processing of the supercritical fluid. The fluid storage cavity is sealed, and the pressure of the fluid storage cavity is used to maintain the pressure of the mold forming cavity, thereby reducing the energy consumption of the supercritical fluid pressurization device.

[0040] 2) The upper and lower modules of the mold forming cavity are a combined structure. By simply changing the upper and lower modules, polymers with different structures and sizes can be formed.

[0041] 3) An orifice with a one-way valve is provided above the molding die, which allows fluid to enter the material simultaneously from different parts above the die. This solves the problem of long processing time when the fluid enters the center of the product from the surrounding area during supercritical fluid processing, thus improving processing efficiency.

[0042] 4) A one-way valve is installed in the through hole, so that the supercritical fluid can only enter from this position during the process. When the pressure of the storage chamber and the forming chamber of the mold is the same, the one-way valve closes and seals with the surface of the upper mold. Gas and materials in the forming mold will not flow out from the through hole and thus affect the shape of the formed product. Attached Figure Description

[0043] Figure 1 is a schematic diagram of the overall structure of an embodiment of the present invention.

[0044] Figure 2 is an open structure diagram of the lower mold assembly and the upper mold assembly according to an embodiment of the present invention.

[0045] Figure 3 is an exploded structural diagram of the lower mold assembly according to an embodiment of the present invention.

[0046] Figure 4 is a half-sectional schematic diagram of the lower mold base according to an embodiment of the present invention.

[0047] Figure 5 is a schematic diagram of the lower module structure according to an embodiment of the present invention.

[0048] Figure 6 is a schematic diagram of the upper mold assembly structure according to an embodiment of the present invention.

[0049] Figure 7 is an exploded structural diagram of the upper mold component according to an embodiment of the present invention.

[0050] Figure 8 is a schematic diagram of the upper mold base according to an embodiment of the present invention.

[0051] Figure 9 is a schematic diagram of the upper mold base according to an embodiment of the present invention.

[0052] Figure 10 is a schematic diagram of the structure of the upper mold and intermediate mold according to an embodiment of the present invention.

[0053] Figure 11 is a schematic diagram of the structure of the upper mold and intermediate mold according to an embodiment of the present invention.

[0054] Figure 12 is a schematic diagram of the upper module in an embodiment of the present invention.

[0055] Figure 13 is a schematic diagram of the upper module in an embodiment of the present invention.

[0056] Figure 14 is a front view of the overall structure of an embodiment of the present invention.

[0057] Figure 15 is a half-sectional view of the overall structure of an embodiment of the present invention.

[0058] Figure 16 is an enlarged schematic diagram of part A of Figure 15.

[0059] The attached figures are labeled as follows: 1. Lower mold assembly; 11. Lower mold base; 111. Lower mold placement cavity; 112. Lower mold fixing hole; 113. Lower sealing groove; 114. Lower fixing plate; 12. Lower mold bolt; 13. Lower module; 131. Lower mold mounting hole; 132. Mold forming cavity; 14. Lower sealing ring; 2. Upper mold assembly; 21. Upper mold base; 211. Upper fixing plate; 212. Through hole; 213. Countersunk hole; 214. Connecting pipe; 2 2. Upper sealing ring; 23. Upper mold bolt; 24. Upper mold intermediate mold; 241. Upper mold placement cavity; 242. Upper mold fixing hole; 243. Vent hole; 244. Annular step; 245. Threaded hole; 246. Upper sealing groove; 247. Fluid storage cavity; 25. Upper module; 251. Upper mold mounting hole; 252. Upper mold forming surface; 253. Through hole; 254. Through groove; 26. Intermediate mold bolt; 27. Air inlet pipe; 28. Air outlet pipe. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0061] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0062] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0063] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances. Example

[0064] Referring to Figures 1 to 16, the present invention provides a supercritical foaming device, including a lower mold assembly 1 and an upper mold assembly 2, which together form a mold forming cavity 132.

[0065] The upper mold assembly 2 is also provided with a fluid storage cavity 247 that communicates with the mold forming cavity 132.

[0066] The upper mold assembly 2 is provided with a number of through holes 253 and a through groove 254 for connecting the multiple through holes 253. The fluid storage cavity 247 is connected to the mold forming cavity 132 through the through groove 254 and the through holes 253.

[0067] The mold forming cavity 132 consists of a detachable lower module 13 and a detachable upper module 25.

[0068] The lower module 13 and the upper module 25 are interchangeable structures. By designing different structures and sizes in the lower module 13 and the upper module 25, molded products of different shapes can be formed.

[0069] The lower mold assembly 1 includes a lower mold base 11 and a lower module 13 detachably connected to the lower mold base 11. A mold forming cavity 132 is formed on the lower module 13.

[0070] A lower fixing plate 114 is provided on both sides of the bottom surface of the lower mold base 11. Two elongated grooves are provided at the end of the lower fixing plate 114 away from the lower mold base 11. The two elongated grooves are located at the two ends of the lower fixing plate 114 respectively. The lower film assembly is fixed on the molding machine by bolts passing through the elongated grooves.

[0071] The upper mold assembly 2 includes an upper mold base 21, an upper mold intermediate mold 24 is detachably mounted on the upper mold base 21, an upper module 25 is detachably mounted on the upper mold intermediate mold 24, and an upper mold forming surface 252 is mounted on the upper module 25.

[0072] The upper mold forming surface 252 and the mold forming cavity 132 of the lower module 13 combine to form a closed forming space.

[0073] A lower mold placement cavity 111 is provided on the lower mold base 11, and the lower module 13 is detachably disposed in the lower mold placement cavity 111;

[0074] A number of lower mold fixing holes 112 are evenly distributed around the side wall of the lower mold placement cavity 111.

[0075] The shape of the lower module 13 corresponds to that of the lower mold placement cavity 111. Several lower mold mounting holes 131 corresponding to the lower mold fixing holes 112 are provided circumferentially on its side wall. Both the lower mold fixing holes 112 and the lower mold mounting holes 131 are half holes. The lower mold mounting holes 131 on the lower module 13 and the corresponding lower mold fixing holes 112 form a complete stepped hole after being combined.

[0076] Furthermore, threads are provided at the lower ends of the lower mold fixing hole 112 and the lower mold mounting hole 131, and the lower module 13 and the lower mold base 11 are detachably connected by the lower mold bolts 12 in the lower mold fixing hole 112 and the lower mold mounting hole 131 through the threads.

[0077] An upper fixing plate 211 is fixedly installed on both sides of the bottom surface of the upper mold base 21. Two long grooves are provided at the end of the upper fixing plate 211 away from the upper mold base 21. The two long grooves are located at the two ends of the upper fixing plate 211 respectively. The upper film assembly is fixedly installed on the molding machine by bolts that pass through the long grooves.

[0078] A through hole 212 is provided on the side wall of the upper mold base 21, and an air inlet pipe 27 and an air outlet pipe 28 are fixedly installed at both ends of the through hole 212 respectively.

[0079] A connecting pipe 214 is fixedly installed in the middle of the top surface of the upper mold base 21, and the connecting pipe 214 is connected to the through hole 212;

[0080] A cylindrical fluid storage cavity 247 is opened at the bottom of the upper intermediate mold 24, and the fluid storage cavity 247 is connected to the connecting pipe 214;

[0081] A through vent 243 is provided in the middle of the upper intermediate mold 24, one end of which is connected to the fluid storage cavity 247 and the other end is connected to the guide groove 254.

[0082] The upper module 25 has several through holes 253 and a through groove 254 for connecting the multiple through holes 253. Each through hole 253 is provided with a one-way valve.

[0083] The fluid storage cavity 247 is connected to the mold forming cavity 132 through the vent hole 212, the guide groove 254 and the guide hole 253.

[0084] The pressure in the fluid storage chamber 247 is higher than that in the mold forming chamber 132. The supercritical fluid enters the mold forming chamber 132 from the fluid storage chamber 247. However, due to the one-way valve in the through hole 253, the supercritical fluid can only enter and will not cause the polymer foam material to be squeezed out from the through hole 253, resulting in surface defects of the product.

[0085] A cylindrical upper mold placement cavity 241 is opened at the top of the upper mold intermediate mold 24, and an upper module 25 is detachably installed inside the upper mold placement cavity 241;

[0086] The upper mold placement cavity 241 is cylindrical, and several upper mold fixing holes 242 are evenly distributed around the side wall of the upper mold placement cavity 241.

[0087] The upper module 25 is cylindrical, and its side wall is provided with several upper mold mounting holes 251 corresponding to the upper mold fixing holes 242. Both the upper mold fixing holes 242 and the upper mold mounting holes 251 are half holes. The upper mold mounting holes 251 on the upper module 25 and the corresponding upper mold fixing holes 242 form a complete stepped hole after being combined.

[0088] Furthermore, threads are provided at the lower part of the upper mold fixing hole 242 and the upper mold mounting hole 251, and the upper module 25 and the upper mold base 21 are detachably connected by the upper mold bolts 22 in the upper mold fixing hole 242 and the upper mold mounting hole 251 through the threads.

[0089] The top surface of the lower mold base 11 is also provided with a lower sealing groove 113 with a stepped cross-section. The lower sealing groove 113 is located outside the lower mold placement cavity 111. The lower sealing ring 14 is placed in the lower sealing groove 113 and is placed at the lower part of the lower sealing groove 113.

[0090] An annular step 244 is provided on the top of the upper intermediate mold 24. The annular step 244 is located outside the upper mold placement cavity 241 and corresponds to the upper part of the lower sealing groove 113.

[0091] When the upper mold assembly 2 and the lower mold assembly 1 are closed, the annular step 244 of the upper mold assembly 2 is inserted into the lower sealing groove 113 of the lower mold assembly 1.

[0092] An upper sealing groove 246 is opened on the side of the upper intermediate mold 24 away from the annular step 244, and an upper sealing ring 22 is placed in the upper sealing groove 246.

[0093] The upper mold intermediate mold 24 located outside the upper sealing groove 246 has several threaded holes 245 arranged in a circumferential array, and the upper mold base 21 has several countersunk holes 213 arranged in a circumferential array. The upper mold base 21 and the upper mold intermediate mold 24 are fixedly connected by intermediate mold bolts 26 that pass through the countersunk holes 213 and the threaded holes 245.

[0094] When using this invention, the polymer raw material to be foamed is placed in the mold forming cavity 132, and the upper mold assembly 2 and the lower mold assembly 1 are closed; the air outlet pipe 28 is closed, and the supercritical fluid enters the fluid storage cavity 247 from the air inlet pipe 27, and then enters the mold forming cavity 132 from the fluid storage cavity 247, while the mold is heated at the same time.

[0095] When the gas in the mold forming cavity 132 reaches a certain pressure, the air inlet pipe 27 is closed to maintain the temperature and pressure of the mold forming cavity 132 and to treat the polymer foaming material with supercritical fluid; the air outlet pipe 28 is opened and the supercritical fluid in the fluid storage cavity 247 is automatically released; the molding machine opens the mold and the polymer instantly foams and expands and jumps out of the mold forming cavity 132. Example

[0096] A supercritical foaming method with pressure maintained throughout the entire process, characterized by comprising the following steps:

[0097] S1. Place the polymer raw material to be foamed into the mold chamber and close the upper and lower molds;

[0098] S2. A fluid storage cavity communicating with the mold chamber is provided in the upper mold;

[0099] S3. Place the mold into a hot press molding machine for hot pressing and fill the storage cavity with supercritical fluid at a certain pressure.

[0100] S4. Maintain constant temperature and pressure;

[0101] S5. Release the supercritical fluid in the storage chamber;

[0102] S6. The hot press molding machine opens the mold, and the polymer instantly foams and expands, jumping out of the mold chamber. Example

[0103] A preparation process for a polymer foam material, the preparation process mainly includes the following steps:

[0104] S1. Place the polymer raw material to be foamed into the mold forming cavity 132, and close the upper mold assembly 2 and the lower mold assembly 1.

[0105] S2. The vent pipe 28 is closed, and the supercritical fluid enters the fluid storage chamber 247 from the inlet pipe 27, and then enters the mold forming chamber 132 from the fluid storage chamber 247, while the mold is heated at the same time.

[0106] S3. When the gas in the mold forming cavity 132 reaches a certain pressure, close the air inlet pipe 27, maintain the temperature and pressure of the mold forming cavity 132, and perform supercritical fluid treatment on the polymer foaming material.

[0107] S4. Open the vent pipe 28, and the supercritical fluid in the fluid storage chamber 247 will be automatically released.

[0108] S5. The molding machine opens the mold, and the polymer instantly foams and expands, jumping out from the molding cavity 132 of the mold.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A supercritical foaming device, characterized in that, It includes a lower mold assembly (1) and an upper mold assembly (2), which together form a mold forming cavity (132). The upper mold assembly (2) is also provided with a fluid storage cavity (247) that communicates with the mold forming cavity (132).

2. The supercritical foaming device according to claim 1, characterized in that, The upper mold assembly (2) is provided with a plurality of through holes (253) and a through groove (254) for connecting the plurality of through holes (253). The fluid storage cavity (247) and the mold forming cavity (132) are connected through the through groove (254) and the through holes (253).

3. The supercritical foaming device according to claim 1, characterized in that, The mold forming cavity (132) consists of a detachable lower module (13) and a detachable upper module (25).

4. The supercritical foaming device according to claim 2, characterized in that, The lower mold assembly (1) includes a lower mold base (11) and a lower module (13) detachably connected to the lower mold base (11), wherein a mold forming cavity (132) is formed on the lower module (13). The upper mold assembly (2) includes an upper mold base (21), an upper mold intermediate mold (24) is detachably disposed on the upper mold base (21), an upper module (25) is detachably disposed on the upper mold intermediate mold (24), and an upper mold forming surface (252) is disposed on the upper module (25). The upper mold forming surface (252) and the mold forming cavity (132) of the lower module (13) combine to form a closed forming space.

5. The supercritical foaming device according to claim 4, characterized in that, The lower mold base (11) has a lower mold placement cavity (111) and the lower module (13) is detachably disposed in the lower mold placement cavity (111); The lower mold placement cavity (111) has several lower mold fixing holes (112) evenly distributed around its side wall in the circumferential direction. The shape of the lower module (13) corresponds to that of the lower mold placement cavity (111). Several lower mold mounting holes (131) corresponding to the lower mold fixing holes (112) are arranged circumferentially on its side wall. Both the lower mold fixing holes (112) and the lower mold mounting holes (131) are half holes. The lower mold mounting holes (131) on the lower module (13) and the corresponding lower mold fixing holes (112) form a complete stepped hole after being combined.

6. The supercritical foaming device according to claim 5, characterized in that, A through hole (212) is provided on the side wall of the upper mold base (21), and an air inlet pipe (27) and an air outlet pipe (28) are fixedly provided at both ends of the through hole (212). A connecting pipe (214) is fixedly installed in the middle of the top surface of the upper mold base (21), and the connecting pipe (214) is connected to the through hole (212); The bottom of the upper mold intermediate mold (24) has a cylindrical fluid storage cavity (247), which is connected to the connecting pipe (214); A through vent (243) is provided in the middle of the upper mold intermediate mold (24), one end of which is connected to the fluid storage cavity (247) and the other end is connected to the guide groove (254); The upper module (25) has a plurality of through holes (253) and a through groove (254) for connecting the plurality of through holes (253), and a one-way valve is provided in each of the through holes (253); The fluid storage cavity (247) and the mold forming cavity (132) are connected through the vent (212), the guide groove (254) and the guide hole (253).

7. The supercritical foaming apparatus according to claim 6, characterized in that, The top of the upper mold intermediate mold (24) has a cylindrical upper mold placement cavity (241), and the upper module (25) is detachably installed inside the upper mold placement cavity (241). The upper mold placement cavity (241) is cylindrical, and a plurality of upper mold fixing holes (242) are evenly distributed on the side wall of the upper mold placement cavity (241). The upper module (25) is cylindrical, and its side wall is provided with several upper mold mounting holes (251) corresponding to the upper mold fixing holes (242). The upper mold fixing holes (242) and the upper mold mounting holes (251) are both half holes. The upper mold mounting holes (251) on the upper module (25) and the corresponding upper mold fixing holes (242) are combined to form a complete stepped hole.

8. The supercritical foaming apparatus according to claim 7, characterized in that, The top surface of the lower mold base (11) is also provided with a lower sealing groove (113) with a stepped cross-section. The lower sealing groove (113) is located outside the lower mold placement cavity (111). A lower sealing ring (14) is placed inside the lower sealing groove (113). The lower sealing ring (14) is placed at the lower part of the lower sealing groove (113). The top of the upper mold intermediate mold (24) is provided with an annular step (244), the annular step (244) is located outside the upper mold placement cavity (241), and the annular step (244) corresponds to the upper part of the lower sealing groove (113); The upper mold intermediate mold (24) has an upper sealing groove (246) on the side away from the annular step (244), and an upper sealing ring (22) is placed in the upper sealing groove (246).

9. The supercritical foaming device according to claim 8, characterized in that, The upper mold intermediate mold (24) located outside the upper sealing groove (246) has a plurality of threaded holes (245) arranged in a circumferential array. The upper mold base (21) plate has a plurality of countersunk holes (213) arranged in a circumferential array. The upper mold base (21) and the upper mold intermediate mold (24) are fixedly connected by intermediate mold bolts (26) that pass through the countersunk holes (213) and the threaded holes (245).

10. A supercritical foaming method with continuous pressure maintenance, characterized in that, The method includes the following steps: S1. Place the polymer raw material to be foamed into the mold chamber and close the upper and lower molds; S2. A fluid storage cavity communicating with the mold chamber is provided in the upper mold; S3. Place the mold into a hot press molding machine for hot pressing and fill the storage cavity with supercritical fluid at a certain pressure. S4. Maintain constant temperature and pressure; S5. Release the supercritical fluid in the storage chamber; S6. The hot press molding machine opens the mold, and the polymer instantly foams and expands, jumping out of the mold chamber.

Images