Supercritical fluid assisted polymer devolatilization distributor

Abstract

The invention discloses a supercritical fluid assisted polymer devolatilization distributor. The supercritical fluid assisted polymer devolatilization distributor comprises a gradually-shrinking channel, a throttling channel and a gradually-expanding channel which are connected in sequence. A static mixer is arranged in the throttling channel, the upstream pressure is maintained to be above a supercritical state by increasing fluid resistance, meanwhile, the mixing effect of supercritical fluid and polymer melt is enhanced, stable and uniform foam flow is formed, and pressure fluctuation is avoided; an automatic pressure relief valve assembly is arranged on the upper portion of the divergent channel and composed of a valve opening, a valve cover plate, a spring, an adjusting knob and the like, when the system pressure exceeds a set value, exhaust is automatically started, and controllable pressure relief is achieved. A plurality of rows of flow distribution holes are formed in the lower part of the distributor to ensure that the melt uniformly flows out to form stable melt strips; the problems that traditional equipment is difficult to pressurize and not timely in pressure relief are solved, the supercritical state maintenance, gas-liquid separation and melt forming processes are optimized, the volatile component removal efficiency is improved, the phenomenon that melt strips are broken or accumulated is effectively prevented, and continuous and stable operation of the devolatilization process is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of devolatilization technology, and more specifically to a supercritical fluid-assisted polymer devolatilization distributor. Background Technology

[0002] In the post-processing stage of polymer production, the process of removing unreacted monomers, solvents, oligomers, and other volatile substances from the product is called devolatilization. These residual volatiles in the polymer not only affect the polymer's performance and are detrimental to production safety but also endanger human health. Therefore, devolatilization has become an important step in polymer post-processing.

[0003] Typically, devolatilization employs high-temperature, high-vacuum methods, where heating induces a phase change in the volatiles within the polymer, and the vacuum condition acts as a driving force to remove these volatiles from the polymer melt. However, this method not only consumes a significant amount of energy but also suffers from a sharp increase in viscosity and reduced volatile content in the later stages of the devolatilization process, hindering the diffusion of residual volatiles and resulting in a high volatile content in the final product. Furthermore, it is difficult to remove the devolatilized polymer from the devolatilization container under vacuum conditions. Introducing supercritical fluids into the devolatilization process can effectively address these issues.

[0004] Supercritical fluids are used to assist in polymer devolatilization due to their adjustable solvent strength, high diffusivity, low viscosity, and low surface tension. Supercritical fluid-assisted devolatilization consists of three stages: First, the fluid is heated and pressurized to above its critical temperature and pressure, placing it in a supercritical state. Second, the supercritical fluid is mixed with the polymer, causing the polymer to plasticize and swell. Finally, the system is depressurized; during this process, the swollen polymer gradually returns to its initial state, and the volatiles contained in the polymer escape with the supercritical fluid, achieving the goal of devolatilization.

[0005] During the pressurization stage, the system must reach a pressure above the critical pressure. Taking supercritical carbon dioxide as an example, its critical pressure is 7.38 MPa, which places high demands on the equipment used for supercritical devolatilization. If the pressure does not meet the critical pressure condition, the fluid cannot easily enter the polymer melt to cause swelling, and can only occupy the partial pressure of the gas phase. Simultaneously, if the pressure of the mixed fluid cannot be released in time before entering the devolatilizer, the supercritical carbon dioxide dissolved in the polymer can only be discharged from the flow holes along with the melt. Excessive pressure will cause a large number of bubbles to be generated in the melt strip during the devolatilization process, leading to melt strip breakage, reducing the residence time of the melt in the devolatilizer, and preventing the volatiles in the polymer from fully diffusing, which is detrimental to the devolatilization process.

[0006] The prior art CN202010530796.7 discloses "a method for devolatilization of trans-butadiene rubber," which uses supercritical carbon dioxide to remove residual monomers and dimers from trans-butadiene rubber. This method employs a static extraction approach of first pressurizing and then depressurizing, failing to utilize a distribution device for a continuous devolatilization process. Therefore, insufficient mixing between the polymer and the supercritical fluid results in a long devolatilization time, with a devolatilization cycle of 0.5–4 hours, and low devolatilization efficiency.

[0007] Existing technology CN202021881830.7 discloses a "high-efficiency polystyrene melt devolatilization distributor." This distributor has a horizontally placed cylindrical structure with a feed end at one end and a closed end at the other. Several longitudinally arranged openings with a diameter of 8mm are provided along the lower side of the distributor body from the feed end to the closed end. Because the distributor described in this patent has a fixed opening diameter, its application range is limited, and it is not suitable for other devolatilization conditions, thus significantly limiting its application in actual production.

[0008] Based on the problems of existing distributors, such as difficulty in pressurization during continuous devolatilization and inability to release pressure in time, which leads to the inability of subsequent devolatilization to proceed smoothly, they are not suitable for supercritical assisted devolatilization. Therefore, this invention provides a supercritical fluid-assisted polymer devolatilization distributor. Summary of the Invention

[0009] The purpose of this invention is to provide a supercritical fluid-assisted polymer devolatilization distributor to overcome the problems of pressurization difficulties, untimely depressurization, gas-liquid phase separation and drastic pressure fluctuations in the continuous devolatilization process of existing distributors, and to improve the polymer melt devolatilization efficiency and operational stability.

[0010] The objective of this invention is achieved through the following technical solution: A supercritical fluid-assisted polymer devolatilization distributor includes a front section and a rear section. The front section includes a tapering channel 1 and a throttling channel 2 connected in sequence. The tapering channel 1 has a gradually narrowing inner diameter, while the throttling channel 2 has a fixed inner diameter. A static mixer 3 is disposed inside the throttling channel 2. The rear section includes a expanding channel 4, an automatic pressure relief valve assembly 5, and a flow distribution orifice 7. The expanding channel 4 has a gradually increasing inner diameter and is connected to a cylindrical channel. The automatic pressure relief valve assembly 5 is disposed at the upper end of the cylindrical channel, and the flow distribution orifice 7 is disposed at the lower end. The distributor is entirely disposed inside a devolatilization tank, which is connected to a vacuum system.

[0011] Preferably, the static mixer 3 is selected from one of the SL type, SV type, SK type, SH type or SX type static mixers, or is composed of two or more of them.

[0012] Preferably, the system pressure is controlled by adjusting the inner diameter and / or length of the throttling channel 2, and / or by adjusting the unit length-to-diameter ratio of the static mixer 3. Through reasonable design, adjusting the inner diameter and length of the throttling channel can control the pressure reached by the system to meet different process requirements. For example, reducing the inner diameter of the channel or increasing the channel length can allow the polymer melt of the same flow rate to reach a higher pressure.

[0013] Preferably, the aspect ratio of the unit of the static mixer 3 is 1.0 to 2.0.

[0014] Preferably, the automatic pressure relief valve assembly 5 includes a valve port opening 56, a valve cover plate 55, a spring 52, a valve chamber housing 53, an exhaust port 54, and an adjustment knob 51; the valve port opening 56 is disposed on the distributor; the valve cover plate 55 covers the valve port opening 56; the spring 52 provides preload to the valve cover plate 55; the valve chamber housing 53 covers the outside; the exhaust port 54 is disposed on the valve chamber housing 53; and the adjustment knob 51 is used to adjust the compression of the spring 52.

[0015] Preferably, the opening pressure of the automatic pressure relief valve assembly 5 is set by adjusting the spring compression or replacing the spring with a different elastic modulus using the adjustment knob 51.

[0016] Preferably, the opening pressure of the automatic pressure relief valve assembly 5 is 0.05MPa~0.15MPa.

[0017] Preferably, the aperture of the flow distribution hole 7 is configured to maintain a certain pressure on the melt phase above the hole, so as to ensure that the melt flows out uniformly from all the flow distribution holes.

[0018] This application also claims a devolatilization method using the above-mentioned supercritical fluid-assisted polymer devolatilization distributor, comprising the following steps: The polymer melt containing volatiles is mixed with a supercritical fluid and then conveyed to the front half of the distributor; The mixed fluid enters the throttling channel 2 through the converging channel 1. Under the action of the static mixer 3, the system pressure is maintained above the supercritical pressure, and the supercritical fluid and polymer melt are fully mixed. The mixed fluid enters the gradually expanding channel 4 in the latter half, and the pressure drops below the supercritical pressure. The supercritical fluid changes phase to gaseous state, generating bubbles in the polymer melt. Some of the volatiles are discharged with the gas through the automatic pressure relief valve assembly 5. After being depressurized, the melt enters the devolatilization tank through the flow distribution hole 7 to form melt strips 6, where devolatilization is carried out under vacuum.

[0019] Preferably, the supercritical fluid is supercritical carbon dioxide; the critical temperature is 31.1°C and the critical pressure is 7.38 MPa.

[0020] Preferably, the temperature of the polymer melt is 180℃~240℃, and the mass flow rate is 5kg / h~8kg / h; the polymer melt is transported by a volume pump through a carbon dioxide injection port, a supercritical mixing unit, and a gradually narrowing channel 1 of a distributor.

[0021] The devolatilization method of the supercritical fluid-assisted polymer devolatilization distributor specifically includes the following steps: The supercritical fluid-assisted polymer devolatilization distributor performs supercritical-assisted devolatilization on polymer melts containing volatiles. The supercritical fluid is supercritical carbon dioxide. The polymer melt, transported by a volume pump, passes through the carbon dioxide injection port, the supercritical mixing unit, and the gradually narrowing channel 1 of the distributor. When it reaches the throttling channel 2, the system pressure is 8.5 MPa, which still reaches the supercritical state and allows for thorough mixing with the polymer melt. Supercritical carbon dioxide can cause the polymer to swell, thereby increasing the free volume of the polymer, plasticizing the polymer, and improving the mass transfer rate of volatiles.

[0022] The melt enters the latter half of the supercritical fluid-assisted polymer devolatilization distributor. As it passes through the gradually expanding channel 4, the channel diameter gradually increases, and the pressure gradually decreases to below the critical pressure of carbon dioxide, 7.38 MPa. At this point, the supercritical carbon dioxide dissolved in the polymer changes from a supercritical state to a gaseous state, generating a large number of bubbles in the polymer phase. Some of the volatiles, along with the carbon dioxide, are discharged from the automatic pressure relief valve assembly 5 into the devolatilization tank and extracted by the vacuum pump. The melt in the supercritical fluid-assisted polymer devolatilization distributor forms a melt strip 6 through the lower distribution hole 7 and enters the devolatilization tank under vacuum for devolatilization. Because the gas was released earlier, the melt strip 6 generates a large number of fine bubbles, which does not cause the melt strip to break, thus enhancing the devolatilization process.

[0023] The aforementioned supercritical fluid-assisted polymer devolatilization distributor, through the rational design of the flow orifice size, ensures a certain pressure in the melt phase above the orifice. This pressure allows the melt to flow out smoothly and evenly from each flow orifice. If the flow orifice opening is too large, the melt may flow out from the first few orifices, leaving the subsequent orifices unused. Furthermore, a thicker melt strip entering the devolatilization tank results in an excessively large diffusion path for volatiles, which is detrimental to the devolatilization process and reduces the quality of the final product. If the flow orifice opening is too small, the melt phase pressure will be too high. If the system pressure exceeds the critical pressure, it will hinder the supercritical fluid from being discharged from the vent. After the melt enters the vacuum devolatilization tank, the pressure will suddenly drop, causing the supercritical fluid to undergo a phase change and generate a large amount of gas. This will result in a large number of bubbles being generated in the melt strip, ultimately leading to the breakage of the melt strip.

[0024] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. This invention achieves efficient devolatilization and quality improvement. By optimizing the mixing and separation process of supercritical fluid and polymer, the removal efficiency of volatiles is significantly improved. In the examples, the n-hexane content was reduced from 25% to 46ppm, demonstrating its excellent devolatilization ability, thereby ensuring the purity and quality of the final product. 2. This invention achieves effective pressurization and stable maintenance of the supercritical state. The tapered channel and throttling channel structure in the front half of the distributor utilize fluid resistance to naturally increase the system pressure. By adding a static mixer in the throttling channel, the flow resistance is further increased, which not only helps to reach and maintain the pressure above the supercritical point and ensure that the fluid is in a supercritical state, but also avoids premature pressure drop. 3. This invention improves the mixing and stabilizing flow field. The introduction of a static mixer forces the separation and remixing of the fluid, making the gas-liquid two-phase distribution more uniform and forming a stable "foam flow". This effectively avoids the drastic pressure fluctuations caused by the uneven "plunger flow" and ensures the continuity and stability of the entire devolatilization process. 4. This invention achieves precise pressure relief and melt strip formation protection. The rear half of the distributor is designed with an automatic pressure relief valve assembly, which can automatically open when the system pressure exceeds the set value, giving priority to the discharge of most of the gas and some volatiles. This key step completes the main pressure relief before the melt enters the devolatilization tank, so that the melt strip coming out of the distribution hole only produces fine bubbles, fundamentally avoiding the risk of melt strip breakage due to excessive internal pressure, and ensuring the physical stability of the devolatilization process. 5. This invention is flexible, adjustable, and widely adaptable: Pressure is controllable: By adjusting the size (inner diameter, length) of the throttling channel and the parameters (type, length-to-diameter ratio) of the static mixer, the system pressure can be flexibly controlled to adapt to different process requirements; The pressure relief of this invention is adjustable: by adjusting the knob or replacing the spring, the opening pressure of the automatic pressure relief valve (e.g., 0.05~0.15MPa) can be precisely set, thereby optimizing for different polymer systems and devolatilization conditions, and achieving the best balance between gas release and melt strip forming stability. 6. This invention ensures uniform flow and optimized mass transfer. By rationally designing the aperture of the flow distribution holes, it ensures that the melt above the holes maintains an appropriate pressure, allowing the melt to flow out uniformly from all the flow distribution holes, thus avoiding problems such as uneven flow or blockage of some holes. It forms melt strips of suitable thickness, providing an optimized diffusion path for volatiles, which avoids both excessively long diffusion paths due to excessively thick melt strips and excessively high residual pressure due to excessively small openings. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be made based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the supercritical fluid-assisted polymer devolatilization distributor structure in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the front half of the supercritical fluid-assisted polymer devolatilization distributor in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the automatic pressure relief valve assembly in the supercritical fluid-assisted polymer devolatilization distributor of Embodiment 1 of the present invention; Among them, 1-constriction channel; 2-throttling channel; 3-static mixer; 4-expanding channel; 5-automatic pressure relief valve assembly; 6-melt strip; 7-flow distribution hole; 51-adjusting knob; 52-spring; 53-valve cavity shell; 54-exhaust port; 55-valve cover plate; 56-valve port opening. Detailed Implementation

[0027] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific implementation schemes are now described in detail.

[0028] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0029] Example 1 See appendix Figure 1 ~Appendix Figure 3 This embodiment provides a supercritical fluid-assisted polymer devolatilization distributor, which is used for supercritical-assisted removal of n-hexane from POE melt; The front half of the supercritical fluid-assisted polymer devolatilization distributor includes a tapered channel 1, which is a channel that gradually narrows, with its inner diameter narrowing and extending to a throttling channel 2 with a fixed inner diameter. The inner diameter of the throttling channel 2 is φ8mm and its length is 100mm. The throttling channel 2 is equipped with a static mixer 3. The front half is equipped with an SV-type static mixer with a unit length-to-diameter ratio of 1.5, and the rear half is equipped with an SH-type static mixer with a unit length-to-diameter ratio of 1.5. The throttling channel 2 connects to the rear half of the supercritical fluid-assisted polymer devolatilization distributor, which includes a gradually expanding channel 4, an automatic pressure relief valve assembly 5, and a flow distribution hole 7. The inner diameter of the gradually expanding channel 4 gradually increases to φ51mm, and the subsequent channel is cylindrical. The upper end of the channel is equipped with an automatic pressure relief valve assembly 5, and the lower end is equipped with three rows and three columns of nine flow distribution holes 7, each with a diameter of φ8mm. The supercritical fluid-assisted polymer devolatilization distributor is placed in the devolatilization tank, which is connected to a vacuum pump. During operation, the devolatilization tank is in a negative pressure environment. The automatic pressure relief valve assembly 5 includes a valve port opening 56 disposed on the distributor, a valve cover plate 55 located above the valve port opening 56, a spring 52 providing preload to the valve cover plate 55, a valve cavity housing 53 covering the outside, an exhaust port 54 disposed on the valve cavity housing 53, and an adjustment knob 51 located at the upper end of the spring 52; the pressure during pressure relief can be controlled by adjusting the knob 51 and replacing the spring 52 with different elastic moduli, and the pressure relief pressure is 0.1 MPa;

[0030] The devolatilization method of the supercritical fluid-assisted polymer devolatilization distributor includes the following steps: The supercritical fluid-assisted polymer devolatilization distributor performs supercritical-assisted devolatilization on POE melt containing 25% n-hexane. The supercritical fluid is supercritical carbon dioxide, with a critical temperature of 31.1°C and a critical pressure of 7.38 MPa. POE melt at 220°C and a mass flow rate of 7 kg / h is transported by a volumetric pump through the carbon dioxide inlet, the supercritical mixing unit, and the distributor's converging channel 1. Upon reaching the throttling channel 2, the fluid flow is hindered due to the reduced channel cross-sectional area and the increased flow resistance from the SV-type static distributor. The system pressure at the throttling channel is 8.5 MPa, still in a supercritical state, allowing for thorough mixing of the polymer melt and carbon dioxide. Simultaneously, the SH-type static mixer enhances gas-liquid redispersion and mixing, resulting in uniform phase distribution and a stable foam flow in the latter half of the throttling channel. Supercritical carbon dioxide causes the polymer to swell, increasing its free volume and plasticizing it, thus improving the mass transfer rate of volatiles. The melt enters the latter half of the supercritical fluid-assisted polymer devolatilization distributor. Passing through the gradually expanding channel 4, the channel diameter gradually increases, and the pressure gradually decreases to below the critical pressure of carbon dioxide (7.38 MPa). At this point, the supercritical carbon dioxide dissolved in the polymer changes from a supercritical state to a gaseous state, generating a large number of bubbles in the polymer phase. Some hexane, along with the carbon dioxide, is discharged through the automatic pressure relief valve assembly 5 at the top of the gradually expanding channel. The pressure relief of the automatic pressure relief valve assembly 5 is set to 0.1 MPa. When the system pressure exceeds this set value, the valve cover plate 55 is opened, and the gas enters the devolatilization tank through the exhaust port 54 and is extracted by the vacuum pump. This achieves precise control of the amount of gas released inside the distributor, preventing the melt strip 6 from breaking due to excessive gas or the melt from accumulating inside the distributor due to insufficient gas. In the supercritical fluid-assisted polymer devolatilization distributor, the melt forms a melt strip 6 through the lower flow distribution hole 7 and enters the devolatilization tank under vacuum for devolatilization. Due to the previous release of gas, the melt strip 6 generates a large number of fine bubbles, which does not cause the melt strip to break, thus enhancing the devolatilization process. Analysis of the devolatilized POE sample shows that the n-hexane content is reduced to 46 ppm.

[0031] Comparative Example 1 This comparative example uses a common non-variable diameter polymer devolatilization distributor. The non-variable diameter distributor has a cylindrical structure with a fixed inner diameter of φ51mm. The front half of the distributor has no special structure, and the upper end of the rear half does not have an exhaust port. The lower end has three rows and three columns of nine flow holes, each with a diameter of φ8mm. The distributor is placed in a devolatilization tank, which is connected to a vacuum pump. During operation, the tank is in a negative pressure environment. The devolatilization method of the non-diameter polymer devolatilization distributor includes the following steps: Supercritical assisted devolatilization was performed on POE melt containing 25% n-hexane. The selected supercritical fluid was supercritical carbon dioxide, with a critical temperature of 31.1°C and a critical pressure of 7.38 MPa. The POE melt, at 220°C and a mass flow rate of 7 kg / h, was transported by a volumetric pump through a carbon dioxide inlet and a supercritical mixing unit before directly entering a constant-diameter cylindrical distributor. Because the distributor's inner diameter remained constant, lacking the effect of gradual pressure boosting and throttling mixing, the system pressure was maintained at approximately 4.8 MPa when the melt entered the distributor, lower than that of carbon dioxide. The critical pressure of carbon resulted in poor mixing between the polymer melt and supercritical carbon dioxide. Furthermore, due to the lack of venting design, the pressure could not be released in advance. After the melt was discharged from the flow holes, the pressure dropped sharply, and a large amount of carbon dioxide dissolved in the polymer was discharged, rapidly generating a large number of coarse bubbles. These coarse bubbles easily led to uneven bubble distribution within the melt strip and melt strip breakage during the devolatilization process, thereby reducing the mass transfer efficiency of volatiles. Analysis of the POE sample after devolatilization showed that the n-hexane content was 208 ppm, which was higher than the VOC residue in Example 1. At the same time, the overall devolatilization effect of the product was unstable.

[0032] In summary, the supercritical fluid-assisted polymer devolatilization distributor of the present invention overcomes the shortcomings of existing distributors, such as difficulty in pressurization and untimely pressure release affecting subsequent devolatilization processes. By optimizing the mixing and separation process of supercritical fluid and polymer, it effectively avoids melt strip breakage or accumulation, ensuring a more stable and efficient separation process between polymer and volatiles under supercritical conditions, and improving volatile removal efficiency. The front part of the supercritical fluid-assisted polymer devolatilization distributor of the present invention pressurizes and mixes the melt. Its structure consists of a tapered channel and a throttling channel, with a static mixer installed in the throttling channel. When the volumetric pump pushes the fluid into the pipeline at a fixed flow rate, due to the channel... The reduced cross-sectional area and the obstructing effect of the static mixer create flow resistance, leading to an increase in system pressure. As the fluid travels along the pipeline to the throttling channel, the system pressure gradually decreases, but the pressure inside the throttling channel remains above the critical pressure, causing the injected gas to reach a supercritical state and mix thoroughly with the polymer. Simultaneously, the static mixer, through forced separation and remixing of the fluid, ensures a uniform distribution of the gas and liquid phases, forming a stable foam flow rather than a non-uniform plug flow. This avoids drastic pressure fluctuations within the pipeline and maintains a continuous and stable devolatilization process. Through proper design, adjusting the inner diameter and length of the throttling channel can control the pressure reached by the system to meet different process requirements. For example, reducing the channel inner diameter or increasing the channel length can allow the polymer melt of the same flow rate to reach a higher pressure; the latter half of the supercritical fluid-assisted polymer devolatilization distributor of the present invention is a gradually expanding channel with a gradually increasing inner diameter, which then forms a cylindrical structure. An automatic pressure relief valve assembly is provided above the pipe, and a number of flow distribution holes are provided below. The entire distributor is placed in a vacuum-sealed strip devolatilization tank; due to the increase in the inner diameter of the channel, the system pressure drops below the critical pressure, and the supercritical fluid in the polymer undergoes a phase change, changing from the supercritical state to the gaseous state. A large number of bubbles are generated in the melt phase, and some of the volatiles in the melt are discharged from the automatic pressure relief valve assembly along with a large amount of gas. The automatic pressure relief valve assembly can flexibly adjust the exhaust pressure according to the characteristics of different polymer systems and devolatilization conditions, effectively balancing the gas release and melt strip forming stability, thereby ensuring the continuity of the distributor operation and the devolatilization effect. Since most of the supercritical fluid dissolved in the melt phase has been discharged, the pressure is effectively released. After the melt enters the devolatilization tank through the flow distribution holes, only fine bubbles will be generated, avoiding the risk of melt strip breakage due to excessive pressure. The supercritical fluid-assisted polymer devolatilization distributor of the present invention, through the reasonable design of the flow distribution hole diameter, makes the melt phase above the hole have a certain pressure, which allows the melt to flow out smoothly and evenly from each flow distribution hole.

[0033] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention should be determined by the appended claims.

Claims

1. A supercritical fluid assisted polymer devolatilization distributor characterized by, The distributor comprises a front half and a rear half; the front half comprises a tapered channel (1) and a throttling channel (2) connected in sequence; the tapered channel (1) is a channel with a gradually narrowing inner diameter, and the throttling channel (2) is a channel with a fixed inner diameter; a static mixer (3) is arranged inside the throttling channel (2); the rear half comprises a diverging channel (4), an automatic pressure relief valve assembly (5) and a flow distribution hole (7); the diverging channel (4) is a channel with a gradually increasing inner diameter, which is connected to a cylindrical channel; the upper end of the cylindrical channel is provided with the automatic pressure relief valve assembly (5), and the lower end is provided with the flow distribution hole (7); the distributor is arranged in a devolatilization tank, and the devolatilization tank is connected to a vacuum system; The automatic pressure relief valve assembly (5) comprises a valve port opening (56), a valve cover plate (55), a spring (52), a valve cavity shell (53), an exhaust port (54) and an adjusting knob (51); the valve port opening (56) is arranged on the distributor; the valve cover plate (55) covers the valve port opening (56); the spring (52) provides a pre-tightening force for the valve cover plate (55); the valve cavity shell (53) is covered on the outside; the exhaust port (54) is arranged on the valve cavity shell (53); and the adjusting knob (51) is used to adjust the compression amount of the spring (52).

2. A supercritical fluid assisted polymer devolatilization distributor as recited in claim 1, wherein, The static mixer (3) is selected from one of SL type, SV type, SK type, SH type or SX type static mixers, or is composed of two or more of them.

3. A supercritical fluid assisted polymer devolatilization distributor as recited in claim 1, wherein, The system pressure is controlled by adjusting the inner diameter and / or length of the throttling channel (2), and / or adjusting the unit length-diameter ratio of the static mixer (3).

4. A supercritical fluid assisted polymer devolatilization distributor as recited in claim 1, wherein, The spring compression amount is adjusted by the adjusting knob (51) or a spring with a different elastic modulus is replaced, so as to set the opening pressure of the automatic pressure relief valve assembly (5).

5. A supercritical fluid assisted polymer devolatilization distributor as defined in claim 4, wherein, The opening pressure of the automatic pressure relief valve assembly (5) is 0.05 MPa to 0.15 MPa.

6. A supercritical fluid assisted polymer devolatilization distributor as defined in claim 1, wherein, The hole diameter of the flow distribution hole (7) is configured to maintain a certain pressure of the melt phase above the hole, so as to ensure that the melt uniformly flows out from all the flow distribution holes.

7. A devolatilization method using the supercritical fluid-assisted polymer devolatilization distributor according to any one of claims 1 to 6, characterized by, The method comprises the following steps: After the polymer melt containing volatile components is mixed with a supercritical fluid, the mixed fluid is transported to the front half of the distributor; The mixed fluid enters the throttling channel (2) through the tapered channel (1), and under the action of the static mixer (3), the system pressure is maintained above the supercritical pressure, and the supercritical fluid and the polymer melt are fully mixed; The mixed fluid enters the diverging channel (4) of the rear half, the pressure drops below the supercritical pressure, the supercritical fluid phase changes into a gaseous state, bubbles are generated in the polymer melt, and part of the volatile components are discharged with the gas through the automatic pressure relief valve assembly (5); After pressure relief, the melt forms a melt strip (6) through the flow distribution hole (7) and enters the devolatilization tank, and devolatilization is performed in a vacuum environment.

8. The devolatilization process of claim 7, wherein, The supercritical fluid is supercritical carbon dioxide.

9. The devolatilization process of claim 7, wherein, The temperature of the polymer melt is 180℃ to 240℃, and the mass flow rate is 5 kg / h to 8 kg / h.

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