Supercritical fluid assisted polymer devolatilization distributor

Abstract

The application discloses a supercritical fluid assisted polymer devolatilization distributor, which comprises a tapering channel, a throttling channel and a diverging channel connected in sequence. The throttling channel is provided with a static mixer, which can maintain the upstream pressure above the supercritical state by increasing the fluid resistance, and can strengthen the mixing effect of the supercritical fluid and the polymer melt, form a stable and uniform foam flow and avoid pressure fluctuation. The upper part of the diverging channel is provided with an automatic pressure relief valve assembly, which is composed of a valve port opening, a valve cover plate, a spring and an adjusting knob. When the system pressure exceeds the set value, the automatic pressure relief valve assembly can automatically open the exhaust to realize controllable pressure relief. The lower part of the distributor is provided with multiple rows of flow holes, which can ensure that the melt uniformly flows out to form a stable melt strip. The application solves the problems of difficult pressurization and untimely pressure relief of the traditional equipment, optimizes the supercritical state maintenance, gas-liquid separation and melt forming process, improves the devolatilization efficiency, effectively prevents the melt strip from being broken or accumulated, and ensures the continuous and stable operation of the devolatilization process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of devolatilization, and particularly relates to a supercritical fluid assisted polymer devolatilization distributor. BACKGROUND

[0002] In the post-processing step of polymer production, the process of removing unreacted monomers, solvents, oligomers and other volatile substances in the product is called devolatilization. These volatile substances remaining in the polymer not only affect the performance of the polymer, but also are harmful to production safety and human health. Therefore, devolatilization is an important step in the post-processing of polymers.

[0003] Generally, the devolatilization adopts a high-temperature and high-vacuum removal method, that is, the volatile substances in the polymer are made to change phase by heating, and the volatile substances in the polymer melt are removed by taking the vacuum condition as the driving force of the devolatilization process. However, this method not only consumes a large amount of energy, but also in the later stage of the devolatilization process, the volatile content is reduced, and the viscosity of the system is sharply increased, which hinders the diffusion of the residual volatile substances, resulting in a high volatile content in the final product. On the other hand, it is difficult to discharge the polymer after devolatilization from the devolatilization container under vacuum conditions. The addition of supercritical fluid assistance in the devolatilization process can effectively solve the above problems.

[0004] The supercritical fluid is used to assist the devolatilization of the polymer due to its adjustable solvent strength, high diffusivity, low viscosity and low surface tension. The supercritical fluid assisted devolatilization is divided into three stages: first, the fluid is heated and pressurized to above the critical temperature and critical pressure, and the fluid is in a supercritical state; second, the supercritical fluid is mixed with the polymer, and the polymer is plasticized and swelled; and finally, the system is depressurized, and the swelled polymer gradually returns to the initial state during the depressurization process, and the volatile substances contained in the polymer will overflow the polymer with the supercritical fluid, achieving the purpose of devolatilization.

[0005] In the pressurization stage, the system needs to reach above the critical pressure. Taking the common supercritical carbon dioxide as an example, its critical pressure is 7.38 MPa, which has a high requirement for the equipment of supercritical devolatilization. If the pressure cannot meet the critical pressure condition, the fluid cannot enter the inside of the polymer melt to make it swell, and can only occupy the gas phase partial pressure. At the same time, if the pressure of the mixed fluid cannot be released in time before entering the devolatilization device, the supercritical carbon dioxide dissolved in the polymer can only be discharged from the flow hole together with the melt. The high pressure will cause a large number of bubbles in the melt strip during the devolatilization process, thereby causing the melt strip to break, reducing the residence time of the melt in the devolatilization device, and making the volatile substances in the polymer not fully diffuse, which is not conducive to the devolatilization process.

[0006] The prior art CN202010530796.7 discloses a "trans-polybutadiene rubber devolatilization method", which uses supercritical carbon dioxide to remove the residual monomers and dimers in trans-polybutadiene rubber. This method uses a static extraction method of first increasing pressure and then decreasing pressure, and cannot use a distribution device for continuous devolatilization process. Therefore, the mixing between the polymer and the supercritical fluid is insufficient, resulting in a long devolatilization time of 0.5-4h and low devolatilization efficiency.

[0007] The prior art CN202021881830.7 discloses a "high-efficiency polystyrene melt devolatilization distributor", which is a horizontally placed cylindrical structure. One end is the feed end and the other end is the closed end. A plurality of longitudinally arranged openings are arranged on the lower side of the distributor body from the feed end to the closed end, and the opening diameter is 8mm. Since the distributor described in this patent fixes the opening diameter, its application range is limited, and it is not suitable for other devolatilization conditions, and has great limitations in actual production.

[0008] Based on the problems of existing distributors in continuous devolatilization process, such as difficulty in increasing pressure, inability to timely release pressure, and subsequent devolatilization cannot proceed smoothly, etc., which cannot be applied to supercritical auxiliary devolatilization, the present application provides a supercritical fluid auxiliary polymer devolatilization distributor. SUMMARY

[0009] The purpose of the present application is to provide a supercritical fluid auxiliary polymer devolatilization distributor to overcome the problems of existing distributors in continuous devolatilization process, such as difficulty in increasing pressure, inability to timely release pressure, gas-liquid phase separation, and pressure fluctuation, and to improve the devolatilization efficiency and running stability of polymer melt.

[0010] The purpose of the present application is achieved by the following technical solutions:

[0011] A supercritical fluid auxiliary polymer devolatilization distributor, 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 turn; the tapered channel 1 is a channel with gradually narrowing inner diameter, and the throttling channel 2 is a channel with fixed inner diameter; a static mixer 3 is arranged inside the throttling channel 2; the rear half comprises a gradually expanding channel 4, an automatic pressure relief valve assembly 5 and a flow distribution hole 7; the gradually expanding channel 4 is a channel with gradually increasing inner diameter, which is connected with a cylindrical channel; the automatic pressure relief valve assembly 5 is arranged at the upper end of the cylindrical channel, and the flow distribution hole 7 is arranged at the lower end of the cylindrical channel; the distributor as a whole is arranged in a devolatilization tank, and the devolatilization tank is connected with a vacuum system.

[0012] Preferably, 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.

[0013] Preferably, 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; by 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 channel inner diameter or increasing the channel length can make the same flow of polymer melt reach a higher pressure.

[0014] Preferably, the unit length-diameter ratio of the static mixer 3 is 1.0-2.0.

[0015] Preferably, the automatic pressure relief valve assembly 5 includes a valve port opening 56, a valve cover plate 55, a spring 52, a valve cavity shell 53, an exhaust port 54, and an adjustment knob 51; the valve port opening 56 is provided 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 externally; the exhaust port 54 is provided on the valve cavity shell 53; and the adjustment knob 51 is used to adjust the compression amount of the spring 52.

[0016] Preferably, the opening pressure of the automatic pressure relief valve assembly 5 is set by adjusting the spring compression amount through the adjustment knob 51 or replacing springs with different elastic moduli.

[0017] Preferably, the opening pressure of the automatic pressure relief valve assembly 5 is 0.05-0.15 MPa.

[0018] Preferably, the hole diameter of the flow distribution hole 7 is configured to maintain a certain pressure of the melt phase above the hole to ensure that the melt flows uniformly from all the flow distribution holes.

[0019] The present application also claims a devolatilization method using the above supercritical fluid assisted polymer devolatilization distributor, comprising the following steps:

[0020] After mixing the polymer melt containing volatile components with the supercritical fluid, the mixed fluid is transported to the front half of the distributor;

[0021] The mixed fluid enters the throttling channel 2 through the converging 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;

[0022] The mixed fluid enters the diverging channel 4 in 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;

[0023] The devolatilized melt passes through the flow distribution hole 7 to form a melt strip 6 into a devolatilization tank, and devolatilization is carried out in a vacuum environment.

[0024] Preferably, the supercritical fluid is supercritical carbon dioxide; the critical temperature is 31.1°C, and the critical pressure is 7.38 MPa.

[0025] Preferably, the temperature of the polymer melt is 180-240°C, and the mass flow rate is 5-8 kg / h; the polymer melt is transported by the volume pump, passes through the carbon dioxide filling port, the supercritical mixing unit, and the tapered channel 1 of the distributor.

[0026] The supercritical fluid-assisted polymer devolatilization distribution device specifically includes the following steps:

[0027] The supercritical fluid-assisted polymer devolatilization distribution device is used for supercritical-assisted devolatilization of a polymer melt containing volatile components. The supercritical fluid is supercritical carbon dioxide. The polymer melt is transported by the volume pump, passes through the carbon dioxide filling port, the supercritical mixing unit, and the tapered channel 1 of the distributor, and reaches the throttling channel 2, at which the system pressure is 8.5 MPa, still in a supercritical state, and fully mixed with the polymer melt. The supercritical carbon dioxide can swell the polymer, thereby increasing the free volume of the polymer, plasticizing the polymer, and improving the mass transfer rate of the volatile components.

[0028] After the melt enters the second half of the supercritical fluid-assisted polymer devolatilization distribution device, it passes through the gradually expanding channel 4, the diameter of which gradually increases, and the pressure gradually decreases to below the critical pressure of carbon dioxide, i.e., 7.38 MPa. At this time, the supercritical carbon dioxide dissolved in the polymer changes from a supercritical state to a gaseous state, a large number of gas bubbles are generated in the polymer phase, and part of the volatile components and carbon dioxide are discharged from the automatic pressure relief valve assembly 5 into the devolatilization tank and then pumped out by the vacuum pump. The melt in the supercritical fluid-assisted polymer devolatilization distribution device forms melt strips 6 through the flow distribution holes 7 below and enters the devolatilization tank in a vacuum environment for devolatilization. Because the gas has been released, a large number of fine gas bubbles are generated in the melt strips 6, which do not cause the melt strips to break, thereby strengthening the devolatilization process.

[0029] The supercritical fluid-assisted polymer devolatilization distribution device is designed to have a certain pressure in the melt phase above the flow distribution holes, which allows the melt to smoothly flow out of each flow distribution hole. If the flow distribution holes are too large, the melt may flow out of the first few flow distribution holes, and the subsequent flow distribution holes are not utilized. In addition, the melt strips entering the devolatilization tank are thick, which makes the diffusion path of the volatile components too large, is not conducive to the devolatilization process, and reduces the quality of the final product. If the flow distribution holes are too small, the pressure in the melt phase is too high. If the system pressure is greater than the critical pressure, the supercritical fluid cannot be discharged from the exhaust hole. After the melt enters the vacuum devolatilization tank, the pressure suddenly decreases, the supercritical fluid changes phase to generate a large amount of gas, a large number of gas bubbles are generated in the melt strips, and the melt strips are eventually broken.

[0030] Thanks to the above technical solution, the present application has the following beneficial effects compared with the prior art:

[0031] 1. The present application realizes efficient devolatilization and quality improvement. By optimizing the mixing and separation process of supercritical fluid and polymer, the devolatilization efficiency is significantly improved. In the examples, the content of n-hexane is reduced from 25% to 46 ppm, which proves its excellent devolatilization capacity, thereby ensuring the purity and quality of the final product;

[0032] 2. The present application realizes effective pressurization and stable maintenance of supercritical state. The tapered channel and throttling channel structure in the front half of the distributor naturally raises the system pressure using fluid resistance. 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, ensuring that the fluid is in a supercritical state, but also avoids premature pressure drop;

[0033] 3. The present application improves the mixing and stable flow field. The introduction of static mixers forcibly divides and remixes the fluid, making the gas-liquid two-phase distribution more uniform and forming a stable "foam flow". This effectively avoids the pressure fluctuations caused by uneven "plug flow", ensuring the continuity and stability of the entire devolatilization process;

[0034] 4. The present application realizes precise pressure relief and melt strip forming protection. The automatic pressure relief valve assembly is designed in the back half of the distributor, which can automatically open when the system pressure exceeds the set value, preferentially discharging most of the gas and part of the volatile matter. This key step completes the main pressure relief before the melt enters the devolatilization tank, so that the melt strip coming out of the flow distribution hole only produces fine small bubbles, fundamentally avoiding the risk of melt strip rupture caused by excessive internal pressure, ensuring the physical stability of the devolatilization process;

[0035] 5. The present application has flexible adjustment and wide adaptability: pressure controllable: by adjusting the size (inner diameter, length) of the throttling channel and the parameters (type, length-diameter ratio) of the static mixer, the system pressure can be flexibly controlled to adapt to different process requirements;

[0036] The present application has adjustable pressure relief pressure: by adjusting the knob or replacing the spring, the opening pressure of the automatic pressure relief valve (such as 0.05~0.15MPa) can be accurately set, thereby optimizing for different polymer systems and devolatilization conditions, achieving the best balance between gas release amount and melt strip forming stability;

[0037] 6、The present application guarantees uniform flow and optimized mass transfer, by reasonably designing the aperture of the flow distribution hole, ensuring that the melt above the hole maintains appropriate pressure, so that the melt can uniformly flow out of all flow distribution holes, avoiding uneven flow or plugging of some holes; forming a melt strip of appropriate thickness, providing an optimized diffusion path for volatile components, avoiding both excessively long diffusion paths due to excessively thick melt strips and excessively high residual pressure due to excessively small openings. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical features, objectives and effects of the embodiments of the present application, the drawings needed in the description of the embodiments or prior art will be briefly introduced. Obviously, some of the drawings described below are some embodiments of the present application, and other drawings can also be prepared by those skilled in the art without creative labor on the basis of these drawings.

[0039] Figure 1 is a schematic diagram of the structure of the supercritical fluid assisted polymer devolatilization distributor of embodiment 1 of the present application;

[0040] Figure 2 is a schematic diagram of the structure of the front half of the supercritical fluid assisted polymer devolatilization distributor of embodiment 1 of the present application;

[0041] Figure 3 is a schematic diagram of the structure of the automatic pressure relief valve assembly of the supercritical fluid assisted polymer devolatilization distributor of embodiment 1 of the present application;

[0042] Wherein, 1-tapered channel; 2-throttle channel; 3-static mixer; 4-tapered 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 DESCRIPTION

[0043] In order to have a clearer understanding of the technical features, objectives and effects of the present application, the specific implementation schemes will be described in detail.

[0044] The present application will be further described below in conjunction with the embodiments, but the present application 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 indicated are the conventional conditions in the industry. The technical features involved in each embodiment of the present application can be combined with each other as long as there is no conflict.

[0045] Example 1

[0046] Referring to the drawings Figure 1 ~Appendix Figure 3The embodiment provides a supercritical fluid assisted polymer devolatilization distributor used for supercritical assisted removal of n-hexane in a POE melt.

[0047] The front half of the supercritical fluid assisted polymer devolatilization distributor comprises a tapered channel 1 which is a gradually narrowing channel, and the inner diameter is narrowed and extended to a throttling channel 2 with a fixed inner diameter, the inner diameter of the throttling channel 2 is φ8 mm, and the length is 100 mm.

[0048] The throttling channel 2 is internally provided with a static mixer 3, the front half of which is provided with an SV type static mixer, and the unit length-diameter ratio is 1.5, and the rear half is provided with an SH type static mixer, and the unit length-diameter ratio is 1.5.

[0049] The throttling channel 2 is connected to the rear half of the supercritical fluid assisted polymer devolatilization distributor, and the rear half comprises a diverging channel 4, an automatic pressure relief valve assembly 5 and a flow distribution hole 7.

[0050] The inner diameter of the diverging channel 4 gradually increases to φ51 mm, and the subsequent channel is in a cylindrical shape, the upper end of the channel is provided with the automatic pressure relief valve assembly 5, and the lower end is provided with three rows and three columns of nine flow distribution holes 7, each of which has a diameter of φ8 mm; the supercritical fluid assisted polymer devolatilization distributor is placed in a devolatilization tank, the devolatilization tank is connected with a vacuum pump, and the devolatilization tank is in a negative pressure environment during work.

[0051] The automatic pressure relief valve assembly 5 comprises a valve port opening 56 arranged on the distributor, a valve cover plate 55 located above the valve port opening 56, a spring 52 providing pre-tightening force for the valve cover plate 55, a valve cavity shell 53 coated on the outside, an exhaust port 54 arranged on the valve cavity shell 53, and an adjusting knob 51 located at the upper end of the spring 52; the pressure at the time of pressure relief can be controlled by adjusting the adjusting knob 51 and replacing the spring 52 with different elastic modulus, and the pressure relief pressure is 0.1 MPa.

[0052] The devolatilization method of the supercritical fluid assisted polymer devolatilization distributor comprises the following steps:

[0053] The supercritical fluid assisted polymer devolatilization distributor is used for supercritical fluid assisted devolatilization of POE melt containing 25% n-hexane, the supercritical fluid is supercritical carbon dioxide, the critical temperature is 31.1°C, and the critical pressure is 7.38 MPa; the POE melt with a temperature of 220°C and a mass flow of 7 kg / h is transported under the action of the volume pump, passes through the carbon dioxide filling port, the supercritical mixing unit, the tapered channel 1 of the distributor, and reaches the throttling channel 2; due to the decrease of the channel cross-sectional area and the increase of the flow resistance of the SV type static distributor, the fluid flow is hindered, the system pressure is 8.5 MPa when the fluid flows through the throttling channel, and the system is still in a supercritical state, so that the polymer melt and the carbon dioxide are fully mixed in the process. At the same time, the SH type static mixer can strengthen the gas-liquid redispersion and mixing effect, so that the two phases are uniformly distributed, and a stable foam flow is formed in the latter half of the throttling channel; the supercritical carbon dioxide can swell the polymer, thereby increasing the free volume of the polymer, plasticizing the polymer, and improving the mass transfer rate of the volatile components;

[0054] After the melt enters the latter half of the supercritical fluid assisted polymer devolatilization distributor, the melt passes through the gradually expanding channel 4, the channel diameter gradually increases, and the pressure gradually decreases to below the critical pressure 7.38 MPa of carbon dioxide; at this time, the supercritical carbon dioxide dissolved in the polymer changes from a supercritical state to a gaseous state, a large number of gas bubbles are generated in the polymer phase, and part of the n-hexane is discharged together with the carbon dioxide through the automatic pressure relief valve assembly 5 at the upper part of the gradually expanding channel; the pressure relief pressure of the automatic pressure relief valve assembly 5 is set to 0.1 MPa. When the system pressure exceeds the set value, the valve cover plate 55 is pushed open, the gas enters the devolatilization tank through the exhaust port 54 and is pumped out by the vacuum pump, so as to realize accurate control of the amount of gas released from the inside of the distributor, and avoid the breakage of the melt strip 6 due to excessive gas or the accumulation of the melt in the distributor due to insufficient gas;

[0055] The melt in the supercritical fluid assisted polymer devolatilization distributor forms a melt strip 6 through the flow distribution holes 7 below, and enters the devolatilization tank in a vacuum environment for devolatilization; due to the release of gas, a large number of fine gas bubbles are generated in the melt strip 6, and the melt strip will not be broken, thereby strengthening the devolatilization process; the n-hexane content in the POE sample after devolatilization is reduced to 46 ppm.

[0056] Comparative Example 1

[0057] The comparative example uses a common non-variable-diameter polymer devolatilization distributor; the non-variable-diameter distributor has a cylindrical structure, the inner diameter is fixed at φ51 mm, there is no special structure in the front half of the distributor, no exhaust hole is arranged at the upper end of the rear half of the distributor, and three rows and three columns of a total of nine flow distribution holes are arranged below the lower end; the distributor is placed in the devolatilization tank, the devolatilization tank is connected with a vacuum pump, and the tank is in a negative pressure environment during work;

[0058] The devolatilization method of the variable-diameter-free polymer devolatilization distributor comprises the following steps:

[0059] Supercritical-assisted devolatilization was carried out on a POE melt containing 25% n-hexane. Supercritical carbon dioxide was selected as the supercritical fluid, the critical temperature was 31.1°C, and the critical pressure was 7.38 MPa. The POE melt with a temperature of 220°C and a mass flow rate of 7 kg / h was transported by a volume pump, passed through the carbon dioxide filling port and the supercritical mixing unit, and then directly entered the variable-diameter-free cylindrical distributor. Since the inner diameter of the distributor remained unchanged, there was a lack of the role of gradual contraction and throttling mixing in the front section. When the melt entered the distributor, the system pressure was maintained at about 4.8 MPa, which was lower than the critical pressure of carbon dioxide, and the mixing effect between the polymer melt and the supercritical carbon dioxide was poor. Moreover, due to the lack of vent hole design, the pressure could not be released in advance, and after the melt was discharged from the flow hole, the pressure dropped sharply, a large amount of carbon dioxide dissolved in the polymer was discharged, a large amount of coarse bubbles was quickly generated, coarse bubbles were easy to cause uneven bubble distribution in the melt strip during the devolatilization process, the melt strip was prone to breakage, and thus the mass transfer efficiency of the volatile matter was reduced. After devolatilization, the analysis of the POE sample showed that the content of n-hexane was 208 ppm, which was higher than that of Example 1, and the overall devolatilization effect of the product was unstable.

[0060] In summary, the supercritical fluid assisted polymer devolatilization distributor of the present application can overcome the problems of difficult pressurization, delayed pressure relief and the like of the existing distributor, and effectively avoid the fracture or accumulation of the melt strip by optimizing the mixing and separation process of the supercritical fluid and the polymer, so as to ensure the separation process of the polymer and the volatile under the supercritical condition to be more stable and efficient, and improve the devolatilization efficiency. The front half of the supercritical fluid assisted polymer devolatilization distributor of the present application plays a pressurization and mixing role on the melt, and is composed of a tapered channel and a throttling channel, and a static mixer is arranged in the throttling channel. When the volume pump pushes the fluid into the pipeline at a fixed flow rate, due to the reduction of the channel cross-sectional area and the blocking effect of the static mixer, flow resistance is generated, the pressure in the system rises, the fluid extends along the pipeline to the throttling channel, the pressure of the system gradually decreases, but the internal pressure of the throttling channel is still above the critical pressure, so that the injected gas reaches the supercritical state and is fully mixed with the polymer. At the same time, the static mixer can make the gas-liquid two-phase uniformly distributed by forced division and re-mixing, so as to form a stable foam flow instead of an uneven plug flow, thereby avoiding the sharp fluctuation of the pressure in the pipeline and maintaining the continuity and stability of the devolatilization process. Through reasonable design, the internal diameter and length of the throttling channel can be adjusted to control the pressure reached by the system, so as to meet different process requirements. For example, reducing the internal diameter of the channel or increasing the length of the channel can make the polymer melt of the same flow rate reach a higher pressure. The rear half of the supercritical fluid assisted polymer devolatilization distributor of the present application is a gradually expanding channel with gradually increasing internal diameter, and the subsequent structure is cylindrical. An automatic pressure relief valve assembly is arranged above the pipeline, and a plurality of flow distribution holes are arranged below the pipeline. The distributor as a whole is placed in a devolatilization tank for falling strip devolatilization under vacuum. Due to the increase of the internal diameter of the channel, the pressure of the system decreases to below the critical pressure, the supercritical fluid in the polymer changes from the supercritical state to the gaseous state, a large amount of gas bubbles are generated in the melt phase, and part of the volatile in the melt is discharged together with a large amount of gas from the automatic pressure relief valve assembly. The automatic pressure relief valve assembly can flexibly adjust the exhaust pressure according to the characteristics of different polymer systems and devolatilization conditions, so as to effectively balance the gas release amount and the stability of the melt strip forming, thereby ensuring the continuity and devolatilization effect of the distributor operation. Since most of the supercritical fluid dissolved in the melt phase has been discharged, the pressure is effectively released, and only fine and small gas bubbles are generated when the subsequent melt enters the devolatilization tank through the flow distribution holes, so as to avoid the risk of fracture of the melt strip caused by excessive pressure. The supercritical fluid assisted polymer devolatilization distributor of the present application can make the melt phase above the flow distribution holes have a certain pressure by reasonably designing the size of the flow distribution holes, and the pressure can make the melt flow smoothly from each flow distribution hole.

[0061] The above embodiment only expresses one implementation of the present application, which is described in more detail and in more detail, but cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application patent should be subject to the appended claims.

Claims

1. A supercritical fluid-assisted polymer devolatilization distributor, characterized in that, The distributor includes a front half and a rear half; the front half includes a tapering channel (1) and a throttling channel (2) connected in sequence; the tapering 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 provided inside the throttling channel (2); the rear half includes a expanding channel (4), an automatic pressure relief valve assembly (5), and a flow distribution hole (7); the expanding channel (4) is a channel with a gradually increasing inner diameter, which is connected to a cylindrical channel; the automatic pressure relief valve assembly (5) is provided at the upper end of the cylindrical channel, and the flow distribution hole (7) is provided at the lower end; the distributor is installed entirely inside a devolatilization tank, which is connected to a vacuum system; 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) is covered externally; the exhaust port (54) is disposed on the valve chamber housing (53); the adjustment knob (51) is used to adjust the compression of the spring (52); The system pressure is controlled by adjusting the inner diameter and / or length of the throttling channel (2) and / or adjusting the unit length-to-diameter ratio of the static mixer (3); The opening pressure of the automatic pressure relief valve assembly (5) can be set by adjusting the spring compression or replacing the spring with a different elastic modulus using the adjustment knob (51). The opening pressure of the automatic pressure relief valve assembly (5) is 0.05MPa~0.15MPa.

2. The supercritical fluid-assisted polymer devolatilization distributor as described in claim 1, characterized in that, 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.

3. The supercritical fluid-assisted polymer devolatilization distributor as described in claim 1, characterized in that, The aperture of the flow orifice (7) is configured to maintain a certain pressure on the melt phase above the orifice, so as to ensure that the melt flows out uniformly from all the flow orifices.

4. A method for devolatilization using a supercritical fluid-assisted polymer devolatilization distributor as described in any one of claims 1 to 3, characterized in that, Includes 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, the pressure drops below the supercritical pressure, the supercritical fluid phase changes to gaseous state, bubbles are generated in the polymer melt, and some volatiles are discharged with the gas through the automatic pressure relief valve assembly (5); After depressurization, the melt forms a melt strip (6) through the flow distribution hole (7) and enters the devolatilization tank for devolatilization in a vacuum environment.

5. The devolatilization method as described in claim 4, characterized in that, The supercritical fluid is supercritical carbon dioxide.

6. The devolatilization method as described in claim 4, characterized in that, The temperature of the polymer melt is 180℃~240℃, and the mass flow rate is 5kg / h~8kg / h.

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