A continuous physical foaming device for a fluoroelastomer composition

Abstract

The application provides a continuous physical foaming preparation device for fluorine elastomer composition, relates to the technical field of perfluoroether elastomer, and comprises a feeding system, a shearing kneading and mixing system, a discharging system and an extruder which are connected with each other, wherein the feeding system comprises a fluorine elastomer composition feeding port and a foaming medium feeding port, the fluorine elastomer composition feeding port is controlled to feed by a pressing oil cylinder and a feeding pneumatic ball valve; the shearing kneading and mixing system comprises a double-shaft continuous banbury mixer body and a double-shaft tearing machine assembly, the double-shaft tearing machine assembly has a screw rib, two rotors with a speed ratio and relative rotation, and can make the fluorine elastomer compound perform shearing kneading and mixing in a kneading system composed of the two rotors and the two rotors and the banbury chamber wall; the discharging system comprises a discharging chamber foaming medium pressurizing port, is controlled to discharge by a discharging pneumatic ball valve, is extruded through the single-screw machine assembly and is foamed and formed by a forming die, and can prepare fluorine elastomer products with excellent performance.

Description

Technical Field

[0001] This application relates to the field of perfluoroether elastomer technology, specifically to a continuous physical foaming preparation apparatus for a fluoroelastomer composition. Background Technology

[0002] Plastic extruders utilize the relatively good flow properties of plastics, allowing for a relatively large length-to-diameter ratio of the screw. By dividing the screw into sections, different functions can be achieved, such as conveying, melting, homogenizing, foaming medium injection, shearing, back pressure, and extrusion. Therefore, continuous extrusion physical foaming has been successfully used to prepare microporous plastics, such as polyurethane (PU) foam materials, polystyrene (PS) foam materials, polyolefin (PE, PP, and blends) foam materials, and polyvinyl chloride (PVC) foam materials.

[0003] Existing internal mixers offer high production efficiency and short production cycles, but they are still intermittent mixers. Each start-up and shutdown significantly impacts the machine's operating conditions and the temperature of the mixing chamber, leading to a decline in the performance of the mixed products and varying yield rates between adjacent batches. Therefore, intermittent production greatly affects the production line's operational patterns. Rubber extruders, due to their poor flowability, generally have a small length-to-diameter ratio and a short screw; fluoroelastomers and their compositions exhibit even worse flowability. Summary of the Invention

[0004] In view of this, the embodiments of this specification provide a continuous physical foaming preparation apparatus for fluoroelastomer compositions, which realizes continuous physical foaming preparation of microporous fluoroelastomer compositions, with strong shear and mixing capabilities, greatly improving the flowability of fluoroelastomer compounding, and achieving a more thorough and better mixing effect, thereby enabling the preparation of microporous fluoroelastomer compositions with excellent performance.

[0005] The embodiments in this specification provide the following technical solutions:

[0006] A continuous physical foaming preparation apparatus for a fluoroelastomer composition is provided, comprising an interconnected feeding system, a shearing and kneading mixing system, a discharge system, and an extruder. The feeding system includes a fluoroelastomer composition inlet and a foaming medium inlet, with the fluoroelastomer composition inlet controlled by a pressure cylinder and a pneumatic ball valve. The shearing and kneading mixing system includes a twin-shaft continuous internal mixer body and a twin-shaft shredder assembly. The twin-shaft shredder assembly has two rotors with helical ridges, a speed ratio, and opposite rotation, allowing the fluoroelastomer compound to undergo shearing and kneading mixing within the kneading system formed by the two rotors and the mixing chamber wall. The discharge system includes a foaming medium pressurization outlet in the discharge chamber, with discharge controlled by a pneumatic ball valve. The extruder includes a single-screw assembly and a molding die, with the compound extruded through the single-screw assembly and foamed into shape by the molding die.

[0007] In some embodiments, the system further includes an open mill or internal mixer for obtaining the compounded rubber by mixing a thin pass, the open mill or internal mixer being connected to the feeding system.

[0008] In some embodiments, when the pressing cylinder is raised to the upper pressing position, the compound is added to the feeding system. After the air is purged and replaced by the foaming gas inlet, the feeding pneumatic ball valve is closed, and the pressing cylinder presses the compound to the lower pressing position.

[0009] In some embodiments, the twin-shaft continuous internal mixer body includes a primary chamber and a secondary chamber. The compound is conveyed and kneaded in the primary chamber, during which a foaming medium fluid or its supercritical fluid is used to increase its volume. Then it is conveyed to the secondary chamber for further kneading. The heat generated during the kneading process is controlled at a constant temperature by the shaft cooling system and the internal mixer shell heat exchanger. The exhaust gas generated during the kneading process is discharged from the exhaust port from time to time.

[0010] In some embodiments, the shaft cooling system includes a coolant inlet / outlet assembly and a thermostatic liquid inlet / outlet. The coolant inlet / outlet assembly is located on one side of the twin-shaft continuous internal mixer body. The thermostatic liquid inlet / outlet includes a first thermostatic liquid inlet / outlet and a second thermostatic liquid inlet / outlet respectively located on both sides of the single screw assembly.

[0011] In some embodiments, after the saturated or nearly saturated compound is torn by the biaxial shredder assembly, the high-pressure foaming medium reaches a dissolution equilibrium or near dissolution equilibrium with the compound, and then enters the single screw assembly and is conveyed to the discharge constant pressure valve with venting function for extrusion, and is foamed and molded by the molding die.

[0012] In some embodiments, the rotor types of the two rotors include tangential type and meshing type.

[0013] In some embodiments, the length-to-diameter ratio of the two rotors is 0.9:1 to 10:1.

[0014] In some embodiments, the foaming medium in the shearing and kneading mixing system has a pressure of 8-40 MPa, a temperature of 60-120°C, and a mixing time of 5-40 min.

[0015] In some embodiments, a rotary sealing system is further included, comprising a first rotary sealing unit, a second rotary sealing unit, and a third rotary sealing unit. The first and second rotary sealing units are respectively disposed at both ends of the twin-shaft continuous internal mixer body, and the third rotary sealing unit is disposed in the single-screw assembly, so that rotary sealing is achieved in both the chamber of the twin-shaft continuous internal mixer body and the chamber of the single-screw assembly.

[0016] Compared with the prior art, the beneficial effects that the above-mentioned technical solutions adopted in the embodiments of this specification can achieve include at least:

[0017] 1. Effective temperature control of fluoroelastomers is achieved by simultaneously heating and cooling the mixing chamber and rotor: Initial heating at the start of mixing lowers the viscosity of the fluoroelastomer and increases its gas diffusion coefficient, facilitating diffusion. However, during prolonged shearing and kneading, significant heat is generated. The low thermal conductivity of the fluoroelastomer hinders heat exchange, leading to localized temperature increases and uneven mixing. By simultaneously enhancing heat exchange and cooling capacity through shaft cooling of the mixing chamber and the mixing chamber walls, localized scorching and overheating-induced aging of the fluoroelastomer are prevented. Uniform temperature also prevents bubble growth within the elastomer, avoiding expansion and foaming due to uneven heating.

[0018] 2. In a high-pressure, twin-shaft continuous internal mixer, the fluoroelastomer compound is introduced into the gap between two rotors with helical ribs and a speed ratio, rotating in opposite directions. This allows the fluoroelastomer compound to undergo shearing and kneading within a kneading system composed of the two rotors and the walls of the mixing chamber. This results in the compound being subjected to continuous and repeated shearing, tearing, stirring, and friction within the kneading system formed by the rotors and the mixing chamber walls, thereby enhancing shearing and mixing capabilities and achieving a more thorough and effective mixing effect. Furthermore, the use of an interlocking internal mixer appropriately enhances shearing and mixing capabilities and improves cooling. During mixing, the fluoroelastomer surface regeneration rate is fast, and the sheets are thinner, shortening the diffusion distance of the foaming medium within the fluoroelastomer and facilitating rapid achievement of dissolution equilibrium or near-dissolution equilibrium.

[0019] 3. By using a foaming medium to replace air and pressurize, and controlling the temperature of the fluoroelastomer compound, especially the heat generated during internal mixing is carried away by the low-temperature fluid in the internal heat exchanger and / or the heat exchanger in the wall of the mixing chamber, the purpose of maintaining the internal mixing temperature within the specified range is achieved. This can improve the gas diffusion and heat exchange cooling capacity of the fluoroelastomer during internal mixing, prevent local scorching and aging caused by overheating of the fluoroelastomer, and make the mixing effect more uniform. In addition, the pressure is released periodically during the mixing process to release volatiles, while the foaming medium is added to maintain the system pressure. While maintaining the high-pressure environment of the system, the volatiles released during the mixing process are removed in time, forming a high-pressure closed environment. In particular, the rotary sealing method is used to maintain the high-pressure environment of the system and remove the volatiles released during the mixing process in time.

[0020] 4. A highly efficient continuous physical foaming process for preparing microporous fluoroelastomer compositions has been achieved, integrating continuous mixing, extrusion, foaming, and molding. The resulting microporous fluoroelastomer compositions have good mechanical properties, radiation resistance, and resistance to low-concentration ozone corrosion. They can also maintain good performance at high temperatures, making them suitable even for harsh scenarios such as nuclear power plant insulation materials. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the continuous physical foaming preparation device for fluoroelastomer compositions provided in the embodiments of this application. Detailed Implementation

[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0024] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0026] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0027] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0028] Based on the shortcomings described in the background technology, the inventors, through in-depth research, discovered that to achieve continuous extrusion physical foaming of fluoroelastomers, it is necessary to reduce the shear kneading strength while increasing the mixing time, so that the high-pressure foaming medium and the elastomer form a homogeneous or near-homogeneous system at a certain temperature, in order to smoothly complete the subsequent processes of cell nucleation, expansion, and solidification. To achieve continuous foaming, a bi-shaft continuous internal mixer must have five functional parts: a mixing section, a foaming medium section, a connecting section, an extrusion section, and a foaming section. Therefore, the inventors further concluded that to achieve continuous extrusion physical foaming of fluoroelastomers, it is necessary to modify the existing foaming properties used in the mixing process, mainly including the foaming ratio, cell density, cell size, and the mechanical properties of the microporous fluoroelastomer composition.

[0029] Furthermore, based on the definition of foaming ratio or expansion ratio as: foaming ratio = density before foaming (component density) / density after foaming (foamed rubber density), it can be seen that many factors affect foaming performance, including the saturation time of foaming, the mixing temperature of the internal mixer, the pressure of the foaming medium, and nucleating agents. The principle of preparing microporous fluoroelastomers is to form a fluoroelastomer-foaming medium system under certain temperature and pressure conditions by controlling the changes in temperature or pressure to reduce the solubility of the foaming medium in the fluoroelastomer, causing the foaming medium dissolved in the fluoroelastomer to separate phases, nucleate bubbles, and expand under temperature-induced and / or pressure-induced conditions. Unlike the intermittent foaming method for preparing microporous fluoroelastomer compositions, the dissolution and diffusion process of the foaming medium in the fluoroelastomer during continuous physical foaming is dynamically synchronized with the shearing and kneading mixing process of the fluoroelastomer in the internal mixer. This results in rapid surface renewal, short diffusion distance, and is beneficial to heat and mass transfer processes, significantly shortening the time to reach saturation. Temperature control is a critical factor. At low temperatures, the saturation solubility of the foaming medium is high, but the diffusion rate is slow and the time to reach saturation is long. However, at high temperatures, the saturation is limited by the primary and secondary vulcanization temperatures.

[0030] Therefore, this application embodiment develops an improved continuous physical foaming internal mixer system that meets the above requirements. The internal mixer is connected to a single-screw extruder. Fluoroelastics saturated with foaming medium are foamed and expanded in an atmospheric pressure mold through a die. The fluoroelastic compound is placed in a high-pressure continuous foaming internal mixer. After replacing the air with foaming medium, the pressure is increased, and the temperature of the fluoroelastic compound is controlled. The mixture is sheared, kneaded, and mixed. During the mixing process, the pressure is periodically released to release volatiles, while foaming medium is replenished to maintain the system pressure. The high-strength microporous fluoroelastic composition prepared by this system has the ability to resist radiation and low-concentration ozone erosion, good heat resistance and mechanical properties, and can maintain good performance at high temperatures. It can be applied to high-performance materials such as thermal insulation materials for nuclear power plants.

[0031] like Figure 1 As shown, the continuous physical foaming preparation apparatus for fluoroelastomer compositions provided in this application includes an interconnected feeding system, a shearing and kneading mixing system, a discharge system, and an extruder.

[0032] The feeding system is used for feeding fluoroelastomer compositions (such as fluororubber) and foaming media (such as high-pressure or supercritical carbon dioxide or nitrogen). It includes a fluoroelastomer composition inlet 11 and a foaming media inlet 3. The fluoroelastomer composition inlet 1-1 is controlled by a pressure cylinder 2 and pneumatic ball valves 8-1 and 8-2 installed within its cavity. Preferably, the feeding system is also connected to an open mill or internal mixer (such as...). Figure 1 The internal mixer 1 shown obtains a compound by mixing the fluoroelastomer composition with nucleating agent nanoparticles in a thin pass, and then enters a shear kneading mixing system as a continuous foaming system.

[0033] After mixing in the internal mixer 1, the compounded rubber is obtained. The pressure cylinder 2 is raised to position 2-1, and the internal mixer feed pneumatic ball valve is opened. Two feed pneumatic ball valves can be set. The feed pneumatic ball valve 8-1 is located at the upper part of the fluoroelastomer composition feed port 1-1 cavity, and the feed pneumatic ball valve 8-2 is located at the lower part of the fluoroelastomer composition feed port 1-1 cavity. After the compounded rubber is added, the air is purged and replaced by the foaming gas inlet 3. Then, the internal mixer feed pneumatic ball valve 8-1 is closed, and the pressure cylinder is pressed to position 2-2. The pressure is increased to the specified pressure and maintained within a certain range.

[0034] The shearing and kneading mixing system includes a twin-shaft continuous internal mixer body 4 and a twin-shaft shredder assembly 14. The twin-shaft shredder assembly 14 is a twin-shaft continuous internal mixer with two rotors that rotate in opposite directions with a helical ridge and a speed ratio. This allows the fluoroelastomer compound to be sheared and kneaded in the kneading system composed of the two rotors and the walls of the mixing chamber. The shearing and kneading mixing system is driven and controlled by the main motor 12.

[0035] Before starting the twin-shaft continuous internal mixer body 4, the shaft cooling system is first turned on. The shaft cooling system includes a coolant inlet / outlet assembly 5 and a thermostatic liquid inlet / outlet 16. The coolant inlet / outlet assembly 5 is located on one side of the twin-shaft continuous internal mixer body 4. The thermostatic liquid inlet / outlet 16 includes a first thermostatic liquid inlet / outlet 16-1 and a second thermostatic liquid inlet / outlet 16-1 respectively located on both sides of the single screw assembly 17. The first thermostatic liquid inlet / outlet 16-1 and the second thermostatic liquid inlet / outlet 16-1 are used to introduce thermostatic liquid. The twin-shaft continuous internal mixer body 4 includes a primary chamber 20-1 and a secondary chamber 20-2. The mixed rubber is conveyed and kneaded in the primary chamber 20-1, during which foaming medium fluid or its supercritical fluid is used to increase the volume. Then it is conveyed to the secondary chamber 20-2 for further kneading. The heat generated during the kneading process is controlled at a constant temperature by the shaft cooling system and the internal mixer shell heat exchanger (not shown in the figure), so that its temperature is maintained below the primary vulcanization temperature. The exhaust gas generated during the kneading process is discharged from the exhaust port 9 from time to time. Preferably, the exhaust port 9 is equipped with a volatile pressure relief valve (not shown in the figure) and is connected to the exhaust gas treatment device (not shown in the figure) so as to treat the exhaust gas in a timely manner and avoid pollution.

[0036] The discharge system includes a foaming medium pressurization port 13 in the discharge chamber, and discharge from the discharge end 10 is controlled by a pneumatic ball valve 7. The extruder includes a single screw assembly 17 and a molding die 19. The material is extruded through the single screw assembly 17 and foamed by the molding die 19. The extruder is driven by a single screw conveyor motor. Preferably, saturated or nearly saturated rubber compound is torn by a biaxial shredder assembly 14. After the high-pressure foaming medium reaches or is close to dissolution equilibrium with the rubber compound, it enters the single screw assembly 17 and is conveyed to the discharge constant pressure valve 18 with venting function for extrusion. The discharge constant pressure valve 18 can control the pressure through venting. The entire process is temperature-controlled by a constant temperature liquid, and the material is foamed by the molding die 19.

[0037] Preferably, the rotor types of the two rotors in the biaxial tearing machine assembly 14 include tangential and meshing types. More preferably, the length-to-diameter ratio of the two rotors is 0.9:1-10:1. When the length-to-diameter ratio is large, such as 10:1, in order to improve the mixing effect and efficiency of the fluoroelastomer and shorten the dissolution equilibrium time of the foaming medium, the present invention divides the mixing of the material into two stages, namely the first mixing zone located in the primary cavity 20-1 and the second mixing zone located in the secondary cavity 20-2. The mixing process is as follows: the material entering the mixing chamber from the feeding chamber is fed by the rotor shaft. As the rotor shaft screw continuously conveys the material, it enters the first mixing zone for initial mixing. After initial mixing, the material is subjected to compression by subsequent materials, and the second mixing zone... Material from the first mixing zone is gradually fed into the second mixing zone for further mixing to improve its mixing performance. As more material enters, the material from the first mixing zone is forced into the second mixing zone, causing it to move forward. When it reaches the discharge port (i.e., discharge end 10, the opening and closing of the discharge port is controlled by the discharge pneumatic ball valve 7), it flows into the extruder (single screw extruder). The material is then extruded and molded, foamed and expanded in the die under normal pressure, and undergoes secondary vulcanization to obtain the finished product. The residence time of the material in the mixing chamber is greatly influenced by the rate of material input; inversely proportional to the rate of material input, the higher the rate of material entering the mixing chamber, the shorter the residence time.

[0038] In some embodiments, the foaming medium used in the shear-kneading mixing system has a pressure of 8-40 MPa, a temperature of 60-120°C, and a mixing time of 5-40 min. Preferably, the foaming medium has a pressure of 15-35 MPa, a temperature of 80-100°C, and a mixing time of 20 min.

[0039] Preferably, the continuous physical foaming preparation apparatus for fluoroelastomer composition provided in this application embodiment further includes a rotary sealing system. The rotary sealing system includes a first rotary sealing unit 21-1, a second rotary sealing unit 21-2, and a third rotary sealing unit 21-3. The first rotary sealing unit 21-1 and the second rotary sealing unit 21-2 are respectively disposed at both ends of the twin-shaft continuous internal mixer body 4, and the third rotary sealing unit 21-3 is disposed in the single screw assembly 17, so that rotary sealing is achieved in both the chamber of the twin-shaft continuous internal mixer body 4 and the chamber of the single screw assembly 17. For example, it can be a rotary shaft sealing method, specifically a single-end rotary seal, a double-end rotary seal, a multi-spring rotary seal, a lubricating oil seal, a belt rotary seal, a ceramic rotary seal, etc.

[0040] In this specification, similar or identical parts between the various embodiments can be referred to interchangeably, and each embodiment focuses on describing the differences from other embodiments. Furthermore, this specification uses specific terms to describe the embodiments. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0041] Furthermore, unless expressly stated in the claims, the order of processing elements and sequences, the use of numbers and letters, or other names described in this specification are not intended to limit the order of the processes and methods described herein. Although various examples have been discussed in the foregoing disclosure of some embodiments of the invention that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments; rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments described herein. For example, while the system components described above can be implemented by hardware devices, they can also be implemented solely by software solutions, such as installing the described system on existing processing devices or mobile devices.

[0042] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this specification. Such modifications, improvements, and corrections are suggested in this specification and therefore remain within the spirit and scope of the exemplary embodiments described herein.

Claims

1. A continuous physical foaming preparation apparatus for a fluoroelastomer composition, characterized in that, The system includes an interconnected feeding system, a shearing and kneading mixing system, a discharge system, and an extruder. The feeding system includes a fluoroelastomer composition inlet and a foaming medium inlet, with the fluoroelastomer composition inlet controlled by a pressure cylinder and a pneumatic ball valve. The shearing and kneading mixing system includes a twin-shaft continuous internal mixer body and a twin-shaft shredder assembly. The twin-shaft shredder assembly has two rotors with helical ridges, a speed ratio, and opposite rotation, allowing the fluoroelastomer compound to undergo shearing and kneading mixing within the kneading system formed by the two rotors and the mixing chamber wall. The discharge system includes a foaming medium pressurization port in the discharge chamber, with discharge controlled by a pneumatic ball valve. The discharge chamber is located between the twin-shaft continuous internal mixer body and the twin-shaft shredder assembly. The extruder includes a single-screw assembly and a molding die, with extrusion occurring through the single-screw assembly and foaming formed by the molding die. The twin-shaft continuous internal mixer body includes a primary chamber and a secondary chamber. The compound is conveyed and kneaded in the primary chamber, during which a foaming medium fluid or its supercritical fluid is added to increase its volume. Then it is conveyed to the secondary chamber for further kneading. The heat generated during the kneading process is controlled at a constant temperature by the shaft cooling system and the internal mixer shell heat exchanger. The shaft cooling system includes a coolant inlet / outlet assembly and a thermostatic liquid inlet / outlet. The coolant inlet / outlet assembly is located on one side of the twin-shaft continuous internal mixer body. The thermostatic liquid inlet / outlet includes a first thermostatic liquid inlet / outlet and a second thermostatic liquid inlet / outlet respectively located on both sides of the single screw assembly. After the saturated or nearly saturated compound is torn by the biaxial shredder assembly, the high-pressure foaming medium reaches a dissolution equilibrium or near dissolution equilibrium with the compound, and then enters the single screw assembly and is conveyed to the discharge constant pressure valve with venting function for extrusion, and is foamed and formed by the molding die.

2. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 1, characterized in that, It also includes an open mill or internal mixer for obtaining compounded rubber by mixing a thin pass through a mixing mill, wherein the open mill or internal mixer is connected to the feeding system.

3. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 1, characterized in that, When the pressing cylinder is raised to the upper pressing position, the compound is added to the feeding system. After the air is purged and replaced by the foaming gas inlet, the feeding pneumatic ball valve is closed, and the pressing cylinder presses the compound to the lower pressing position.

4. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 1, characterized in that, The exhaust gas generated during the kneading process is discharged from the exhaust port intermittently.

5. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 1, characterized in that, The rotor types of the two rotors include tangential type and meshing type.

6. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 5, characterized in that, The length-to-diameter ratio of the two rotors is 0.9:1-10:

1.

7. The continuous physical foaming preparation apparatus for fluoroelastomer compositions according to claim 1, characterized in that, The foaming medium in the shearing, kneading and mixing system has a pressure of 8-40 MPa, a temperature of 60-120℃, and a mixing time of 5-40 min.

8. The apparatus for continuous physical foaming preparation of fluoroelastomer compositions according to any one of claims 1 to 7, characterized in that, It also includes a rotary sealing system, which comprises a first rotary sealing unit, a second rotary sealing unit, and a third rotary sealing unit. The first and second rotary sealing units are respectively located at both ends of the twin-shaft continuous internal mixer body, and the third rotary sealing unit is located in the single-screw mill assembly, so that rotary sealing is achieved in both the chamber of the twin-shaft continuous internal mixer body and the chamber of the single-screw mill assembly.

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