A continuous dynamic efficient devolatilization method based on a high mass transfer interface polymer / volatile system

Abstract

This invention discloses a continuous dynamic high-efficiency devolatilization method for a polymer / volatile fraction system based on a high mass transfer interface, comprising the following steps: using a single-screw dynamic devolatilizer, adding a polymer solution to the devolatilizer, the polymer solution comprising devolatilized polymer and volatile small molecules, the volatile small molecules including organic solvents, residual monomers, water, or reaction byproducts; the material in the devolatilization section is conveyed and compressed by the screw after devolatilization, and directly leaves the dynamic devolatilizer; or a side-feed extruder is set downstream of the devolatilization section, plastic additives are added to the devolatilized polymer melt, and melt-blended with the raw material polymer at the end of the dynamic single-screw devolatilizer before leaving the dynamic devolatilizer. This invention's continuous dynamic devolatilization method based on a high mass transfer interface is highly efficient, with the high efficiency stemming from the high mass transfer interface, which is derived from the design of the screw and shell structure in the forced flow zone. It can effectively reduce equipment investment and maintenance costs while achieving the same effect.

Description

Technical Field

[0001] This invention relates to the field of polymer production and processing technology, and in particular to a continuous, dynamic, and efficient devolatilization method for polymer / volatile fraction systems based on a high mass transfer interface. Background Technology

[0002] During polymer synthesis, most polymer systems exiting the reactor contain low-molecular-weight components such as residual monomers, organic solvents, water, and reaction byproducts, collectively referred to as volatiles. The content of these volatiles can be as high as tens of percent. The process of removing these volatiles from the polymer bulk is called devolatilization, which can improve the degree of polymerization and performance of the polymer, recover residual monomers and solvents, remove odors, and meet health and environmental requirements. Depending on the application of the polymer product, the target volatile concentration in the devolatilization process can range from several thousand to tens of ppm (parts per million). The energy consumption of the devolatilization process accounts for more than 60% of the total energy consumption in the entire polymer synthesis process. Therefore, efficient devolatilization is an important means to reduce polymer production costs and improve product quality.

[0003] When a polymer system has a high volatile content and low viscosity, a large number of bubbles rapidly form under low pressure. These bubbles expand through liquid-phase mass transfer and aggregation, resulting in flash devolatilization. Flash devolatilization has high heat and mass transfer efficiency, and the process is mainly controlled by phase equilibrium. As the volatile concentration decreases and the viscosity increases, the polymer system undergoes devolatilization through processes such as bubble nucleation, growth, aggregation and merging, and collapse, resulting in foaming devolatilization. Bubble nucleation and growth are the controlling steps of the devolatilization rate, mainly determined by the viscoelasticity and superheat of the system. With further reduction in volatile concentration, only a few or no new bubbles are generated, and devolatilization is controlled by molecular diffusion at the polymer-gas interface. Diffusion-controlled devolatilization is usually carried out under high vacuum conditions. Increasing the mass transfer interface area between the polymer melt and the gas phase and promoting surface renewal are effective means to improve devolatilization efficiency. There are many types of industrial devolatilizers, which can be divided into static devolatilizers without mechanical stirring, mainly for low-viscosity systems, such as flash evaporators and drop-strip devolatilizers; and dynamic rotary devolatilizers, which have rotating elements to transport and mix polymer systems and can handle high-viscosity polymer systems, such as thin-film evaporators and screw devolatilizers. Among them, screw devolatilizers have advantages such as stable conveying, good heat transfer, uniform mixing, and fast surface renewal rate. Moreover, they can effectively handle systems with viscosity differences of several orders of magnitude within a single screw devolatilizer, making them unique among devolatilizers.

[0004] Patent CN 11076524A discloses a static devolatilizer, comprising an upper phase separation chamber and a bottom distributor subunit, performing two-step devolatilization to increase the phase interface area and prolong the residence time during the devolatilization process. However, due to the inability to rapidly renew the surface in the static devolatilizer, it cannot handle polymer systems with high viscosity and low volatile matter concentration. The residual volatile matter concentration of the polymer / volatile matter system treated by the static devolatilizer of this invention is as high as several thousand ppm, exceeding the requirements for residual volatile matter concentration in most application fields. Patents EP 2168743 and US 2020 / 0215738 disclose a twin-screw dynamic devolatilizer, which uses a kneading section to apply shear force to the polymer melt through a kneading element, diverting the melt stream in the screw channel to generate the mass transfer interface area required for devolatilization and promote surface renewal. However, the high shear stress can lead to polymer degradation and color changes, affecting the quality of polymer products and limiting their application areas. Furthermore, compared to single-screw dynamic devourers, twin-screw dynamic devourers have a more complex structure and higher manufacturing and maintenance costs. Traditional dynamic single-screw devourers also have some unavoidable problems, specifically:

[0005] 1. The mass transfer interface generated by the single-screw dynamic devourer is very small, which severely restricts its devouring efficiency;

[0006] 2. In industrial practice, single-screw dynamic devolatilizers can usually only handle polymer solution raw materials with a volatile content of about 1% or even lower, which limits their application range;

[0007] 3. When the actual working conditions of the pull-out device change, the twin-screw pull-out device can adapt to the new working conditions by adjusting the modular screw element combination, while the single-screw dynamic pull-out device has lower operational flexibility due to its integral screw structure. Summary of the Invention

[0008] The purpose of this invention is to provide a continuous, dynamic, and efficient devolatilization method for polymer / volatile fraction systems based on a high mass transfer interface, thereby solving one or more of the problems in the prior art.

[0009] This invention provides a continuous, dynamic, and efficient devolatilization method for polymer / volatile fraction systems based on high mass transfer interfaces, comprising the following steps:

[0010] When using a single-screw dynamic devolatilizer, a polymer solution is added to the devolatilizer. This polymer solution includes volatile small molecules of the devolatilized polymer, which include organic solvents, residual monomers, water, or reaction byproducts. The material in the devolatilization section is conveyed and compressed by the screw, leaving the devolatilizer directly.

[0011] A side-feed extruder is set up downstream of the devolatilization section to add plastic additives into the polymer melt after devolatilization. The polymer is melt-blended with the polymer at the end of the dynamic single-screw devolatilizer and then leaves the dynamic devolatilizer.

[0012] In some implementations, the dynamic single-screw devourer is provided from the end to the front with a drive motor and gearbox, a rear exhaust section, a feeding section, a first-stage stripping section, a first-stage devouring section, a second-stage stripping section, a third-stage stripping section, a third-stage devouring section, and a conveying / mixing section.

[0013] Among them, the rear exhaust section, the third-stage stripping and the third-stage devolatilization can be omitted as needed.

[0014] In some implementations, during the devolatilization process, the number of stages for post-venting devolatilization and pre-venting devolatilization is selected according to the devolatilization requirements. When the volatile concentration in the polymer solution entering the dynamic single-screw devolatilizer is 5-20% and still has flash evaporation potential, a post-venting stage is set to discharge the volatiles, and the feed stage collects the polymer. When the volatile concentration in the polymer solution entering the dynamic single-screw devolatilizer is ≤2%, it can be selected to directly enter the downstream first-stage stripping stage and the first-stage devolatilization stage through the feed stage.

[0015] In some embodiments, the length L3 of the feed section is 3-15D, preferably 6-8D; the screw at the feed inlet position is a single-start or multi-start deep groove thread with a lead of 0.5-4D, preferably 0.6-1.5D, more preferably 0.9-1.5D, and a groove depth of 0.05-0.4D, preferably 0.1-0.2D;

[0016] The length L2 of the rear exhaust section is 3-15D, preferably 4-6D; it adopts a single-start or multi-start thread, the thread lead is 0.5-4D, preferably 0.9-1.5D, and the depth of the thread groove is 0.05-0.4D, preferably 0.08-0.20D. The depth of the thread groove gradually decreases or remains constant from the feed section to the reducer side. The temperature of the material entering the dynamic degassing device is higher than the boiling point of the volatiles, and the pressure is higher than the corresponding saturation pressure. The pressure of the rear exhaust section is 1-100 kPa, preferably 10-80 kPa, and more preferably 30-60 kPa.

[0017] Where: D is the outer diameter of the screw.

[0018] In some embodiments, the solution after post-gas concentration is compressed and pressurized in the feed section before entering the first-stage stripping zone; the stripping agent is selected from water or N2, CO2; the injection amount of stripping agent upstream of each devolatilization section is 0-2 wt% M, preferably 0.2-1 wt% M, more preferably 0.2-0.5 wt% M; the length of the stripping section is 1.5-5 D, preferably 2-3 D; the screw of the stripping section is equipped with a mixing element, including a pin block or a slotted screw rib; the end of the stripping section is provided with a reverse spiral structure or a damping ring, the diameter of the damping ring is 0.9-1.0 D, preferably 0.96-0.99 D; the width of the damping ring is 0.01-1 D, preferably 0.05-0.2 D.

[0019] Where: M is the mass flow rate of the polymer melt processed by the devolatilizer, kg / hr.

[0020] In some embodiments, the material flowing out of the stripping section enters the space formed by the diversion ring and its pressure block in the forced diversion zone of the shell of the devolatilization section, and then flows out into the screw groove of the screw; the length of the forced diversion zone is 0.1-5D, preferably 0.5-2D;

[0021] The flow divider ring includes, but is not limited to, slit type and porous type. The slit width of the slit type flow divider ring is 0.1-5mm, preferably 0.5-2mm; the slit length is 10-200mm, preferably 20-80mm; the slit spacing is 1-10mm, preferably 2-3mm; the entrance of the slit is chamfered to avoid dead zones on the outer surface of the flow divider ring; the slits are aligned or staggered in the axial direction; the slits can be distributed in a straight line or a spiral in the axial direction.

[0022] The end diameter of the porous flow divider ring is 0.2-10 mm, preferably 0.5-3 mm; the radial hole spacing is 1-10 mm, preferably 2-5 mm; the axial hole spacing is 1-10 mm, preferably 2-5 mm; and the inlet of the holes is chamfered. The holes can be distributed in a straight line or a spiral in the axial direction.

[0023] In some embodiments, the screws at the forced diversion zone and exhaust zone of the devolatilization section are composed of multi-start equal-depth and equal-pitch threads with a length of 1-10D, preferably 5-8D; the thread lead is 1-10D, preferably 2-6D; the number of thread starts is 2-20, preferably 4-12; and the pressure in the exhaust zone is 0.1-80kPa, preferably 0.1-60kPa, more preferably 0.1-20kPa.

[0024] In some embodiments, the single-screw dynamic devourer further includes: a forced diversion zone between the feed section and the exhaust section, the forced diversion zone being a space formed by a diversion ring and its pressure block, the length of the forced diversion zone being 0.1-5D, preferably 0.5-2D;

[0025] The flow divider ring includes, but is not limited to, slit type and porous type. The slit width of the slit type flow divider ring is 0.1-5mm, preferably 0.5-2mm; the slit length is 10-200mm, preferably 20-80mm; the slit spacing is 1-10mm, preferably 2-3mm; the entrance of the slit is chamfered to avoid dead zones on the outer surface of the flow divider ring; the slits are aligned or staggered in the axial direction; the slits can be distributed in a straight line or a spiral in the axial direction.

[0026] The end diameter of the porous flow divider ring is 0.2-10 mm, preferably 0.5-3 mm; the radial hole spacing is 1-10 mm, preferably 2-5 mm; the axial hole spacing is 1-10 mm, preferably 2-5 mm; and the inlet of the holes is chamfered. The holes can be distributed in a straight line or a spiral in the axial direction.

[0027] In some implementations, the screw in the latter part of the exhaust zone conveys and compresses the devolatilized polymer melt, and after pressure is built up, it enters the next stage stripping zone and devolatilization zone;

[0028] The concentration of volatiles in the polymer melt after being devolatilized by the single-screw dynamic devolatilizer is 10-3000 ppm, preferably 100-400 ppm, more preferably 100-200 ppm; the rotational speed of the single screw is 10-300 rpm, preferably 40-200 rpm.

[0029] The material output from the final stage of the devolatilization zone is conveyed and compressed by the screw, and then leaves the dynamic devolatilization unit directly.

[0030] In some implementations, the screw in the latter part of the exhaust zone conveys and compresses the devolatilized polymer melt, and after pressure is built up, it enters the next stage stripping zone and devolatilization zone;

[0031] The concentration of volatiles in the polymer melt after being devolatilized by the single-screw dynamic devolatilizer is 10-3000 ppm, preferably 100-400 ppm, more preferably 100-200 ppm; the rotational speed of the single screw is 10-300 rpm, preferably 40-200 rpm.

[0032] The material output from the final stage of the devolatilization zone is thoroughly mixed with the plastic additives from the side feed before leaving the dynamic devolatilization unit.

[0033] In some embodiments, the plastic additives include antioxidants, UV stabilizers, lubricants, antistatic agents, pigments, etc.

[0034] The present invention has the following beneficial effects:

[0035] 1. A dynamic single-screw devolatilizer is used to devolatilize polymer solution raw materials with a volatile concentration of 5-10% to a volatile concentration of 10-200ppm;

[0036] 2. By designing a novel screw-shell structure for a dynamic single-screw devourer, the mass transfer interface of the dynamic single-screw devourer is significantly improved while retaining the advantage of low shear stress of the single-screw devourer.

[0037] 3. Based on different target volatile concentrations, different polymer diversion internal components are designed. The target devolatification efficiency is achieved by adjusting the mass transfer interface area on the basis of a screw-shell system, effectively reducing the investment and maintenance costs of the equipment. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a dynamic single-screw escapement device;

[0039] Figure 2 This is a schematic diagram of the rear exhaust section screw configuration;

[0040] Figure 3 This is a schematic diagram of the screw configuration in the stripping section;

[0041] Figure 4 This is a schematic diagram of the devolatilization section shell structure;

[0042] Figure 5 This is a schematic diagram of a porous flow divider ring;

[0043] Figure 6A 6B is a schematic diagram of a slit-type splitter ring; 6C is a schematic diagram of a left-handed slit-type splitter ring;

[0044] Figure 7 This is a schematic diagram of the multi-start thread configuration of the devoured section.

[0045] In the diagram: 1. Drive motor and gearbox; 2. Rear exhaust section; 3. Feeding section; 4. First-stage stripping; 5. First-stage devolatilization; 6. Second-stage stripping; 7. Second-stage devolatilization; 8. Third-stage stripping; 9. Third-stage devolatilization; 10. Conveying / mixing section. Detailed Implementation

[0046] The present invention will be further described in detail below through embodiments.

[0047] This invention employs a dynamic single-screw devourer, which, from its end (drive motor / reduction gearbox end) to its front end (head end), is sequentially equipped with a rear exhaust section, a feed section, a primary devouring section (including first-stage stripping), a secondary devouring section (including second-stage stripping), and a tertiary devouring section (including third-stage stripping). Figure 1As shown. The raw material for the dynamic single-screw devolatilizer comes from a polymer solution containing volatiles in the polymerization reactor. In this invention, the dynamic single-screw devolatilizer can handle a solution concentration of up to 20 wt%. To obtain ideal product performance, a side-feed extruder can be installed downstream of the devolatilization section to add plastic additives (such as antioxidants, UV stabilizers, lubricants, antistatic agents, pigments, etc.) into the devolatilized polymer melt, which is then melt-blended with the raw material polymer at the end of the dynamic single-screw devolatilizer. The outlet end of the dynamic single-screw devolatilizer is connected to a granulation device, such as a strip pelletizer or underwater pelletizer. One or more of the following can be connected between the dynamic single-screw devolatilizer and the granulation device: a screen changer, a melt pump, and a start-up valve.

[0048] In the specific devolatilization process, the number of stages (single, two, or three stages) of post-venting devolatilization and pre-venting devolatilization are selected according to the devolatilization requirements. When the volatile content in the polymer solution entering the dynamic single-screw devolatilizer is high (5-20%) and still has flash evaporation potential, a post-venting stage is set up to discharge the volatiles, while the feed stage captures the polymer. When the volatile content in the polymer solution entering the dynamic single-screw devolatilizer is very low (≤2%), it can directly enter the downstream first-stage stripping stage and first-stage devolatilization stage through the feeding stage. The feed stage length L3 is 3-15D (D is the screw diameter), preferably 6-8D. Among them, the range of D for small dynamic devolatilizers is 30-150mm; the range of D for large dynamic devolatilizers is 150-600mm. The screw at the feed inlet is a single- or multi-start, deep-groove thread with a lead of approximately 0.5-4D, preferably 0.6-1.5D, more preferably 0.9-1.5D, and a groove depth of 0.05-0.4D, preferably 0.1-0.2D. For example... Figure 1 As shown, a high-temperature, pressurized polymer solution enters the dynamic single-screw devolatilizer. At the feed position, foam grows rapidly, expanding immediately and filling all screw channels. The length L2 of the post-venting section is 3-15D, preferably 4-6D. A single-start or multi-start thread is used, with a thread lead of 0.5-4D, preferably 0.9-1.5D, and a screw channel depth of 0.05-0.4D, preferably 0.08-0.20D. The screw channel depth gradually decreases or remains constant from the feed section towards the reducer side. The gradual decrease in screw channel depth causes bubble bursting, and the pressure difference causes volatile gases to separate and be discharged through the post-venting port. The viscous flow generated by the screw rotation sends the concentrated solution downstream. The material entering the dynamic single-screw devolatilizer has a temperature higher than the boiling point of the volatiles and a pressure higher than the corresponding saturation pressure. The post-drainage can be devolatilized under normal or negative pressure conditions. The pressure of the post-drainage section is 1-100 kPa (absolute pressure), preferably 10-80 kPa, and more preferably 30-60 kPa.

[0049] After being concentrated by post-gas extraction, the solution is compressed and pressurized in the feed section before entering the first-stage stripping zone 4. The stripping agent is typically water, CO2, or N2, which effectively reduces the partial pressure of volatiles in the gas phase, increases the mass transfer driving force of devolatilization, and also generates bubbles, increasing the gas-liquid mass transfer area and enhancing the devolatilization process. The injection amount of stripping agent upstream of each devolatilization stage is 0-2 wt% M (M is the polymer melt mass flow rate processed by the devolatilizer, kg / hr), preferably 0.2-1 wt% M, more preferably 0.2-0.5 wt% M. The injection area of ​​the stripping agent is selected according to the devolatilization process requirements; it can be injected before the first to third devolatilization stages, or only before the last or two devolatilization stages. The length of the stripping section is 1.5-5D, preferably 2-3D. After the stripping agent is injected, the rotating screw breaks it into a large number of small bubbles that are uniformly dispersed in the polymer. The single screw rotates at a speed of 10-300 rpm, preferably 60-200 rpm. The screw in the stripping section is equipped with mixing elements, such as pin blocks or slotted screw ribs. The end of the stripping section is equipped with a reverse spiral structure or a damping ring, such as... Figure 3 As shown. The diameter of the damping ring is 0.9-1.0D, preferably 0.96-0.99D. The width of the damping ring is 0.01-1D, preferably 0.05-0.2D.

[0050] Due to the obstruction of the reverse spiral structure or damping ring, the material flowing out of the stripping section cannot flow downstream along the screw. Instead, it enters the forced diversion zone within the devolatilization section shell, where it is formed by the diversion ring and its pressure block, and then flows out into the screw groove of the screw. Figure 4 As shown. The flow divider ring forces the melt to flow separately, generating a large melt surface area and providing a gas-liquid interface for devolatilization. Furthermore, the interface generated by the forced flow divider is constantly renewed, significantly improving the devolatilization efficiency of the single-screw dynamic single-screw devolatilizer. The length of the forced flow divider zone is 0.1-5D, preferably 0.5-2D. Typical flow divider rings include, but are not limited to, slit-type and porous types, such as... Figure 5 As shown in Figure 6. The slit width of the slit-type diverter ring is 0.1-5 mm, preferably 0.5-2 mm. The slit length is 10-200 mm, preferably 20-80 mm. The slit spacing (including axial and radial) is 1-10 mm, preferably 2-3 mm. The slit entrance is chamfered to avoid dead zones on the outer surface of the diverter ring. The slits are aligned or staggered axially. The slits can be distributed linearly or spirally axially. The end aperture of the porous diverter ring is 0.2-10 mm, preferably 0.5-3 mm. The radial aperture spacing is 1-10 mm, preferably 2-5 mm. The axial aperture spacing is 1-10 mm, preferably 2-5 mm. The aperture entrance is chamfered. The porous structure can be distributed linearly or spirally axially.

[0051] The screws in the forced diversion zone and exhaust zone of the devouring section are composed of multi-start, equal-depth, equidistant threads, such as... Figure 7 As shown, the length is 1-10D, preferably 5-8D. The thread lead is 1-10D, preferably 2-6D. The number of thread starts is 2-20, preferably 4-12. The number of thread starts is defined as the number of thread apexes on the screw cross-section, which is the most important screw parameter affecting diffusion-controlled devolatilization. As the number of thread starts increases, the diversion of the melt stream in the screw groove increases the interfacial area of ​​the melt film, promoting the surface renewal rate of the melt film. As the screw diameter decreases, increasing the number of thread starts significantly increases the processing difficulty. The pressure (absolute pressure) in the venting zone is 0.1-80 kPa, preferably 0.1-60 kPa, more preferably 0.1-20 kPa. As the volatile content in the feed solution decreases, or as devolatilization proceeds, the operating pressure in the venting zone can be gradually reduced to improve devolatilization efficiency. The concentration of volatiles in the polymer melt after being devolatilized by a dynamic single-screw devolatilizer is 10-3000 ppm, which is determined by factors such as the concentration of volatiles in the raw material solution, the devolatilization technology and the performance requirements of the target product. It is preferably 100-400 ppm, and more preferably 100-200 ppm.

[0052] The screw in the exhaust zone transports and compresses the devolatilized polymer melt, establishing pressure before it enters the next stage stripping and devolatilization zone. The shell, screw configuration, and process conditions of each stripping and devolatilization zone can be identical, or adjusted accordingly as devolatilization progresses and the volatile content in the polymer decreases. The material output from the final devolatilization zone can be transported and compressed by the screw, leaving the dynamic single-screw devolatilizer directly; alternatively, it can be thoroughly mixed with processing aids from the side feed, such as antioxidants, UV stabilizers, lubricants, antistatic agents, and pigments, before leaving the dynamic single-screw devolatilizer.

[0053] Depending on the properties of the polymers being processed, such as rheological properties, and the varying volatile content in the feed solution entering the devolatilizer, the devolatilization efficiency of the dynamic single-screw devolatilizer can be adjusted by selecting different types and sizes of internal components in the splitting ring, thereby improving the operational flexibility of the dynamic single-screw devolatilizer. Compared to traditional single-screw devolatilizers, the post-venting section involved in this invention can significantly increase the volatile concentration in the polymer solution entering the dynamic single-screw devolatilizer, up to a maximum of 20 wt%. When the feed concentration entering the dynamic single-screw devolatilizer is low, the post-venting section may not be required. The selection of the number of devolatilization stages and the operating pressure of the pre- and post-venting zones must comprehensively consider factors such as equipment and process costs, and process stability. As the number of devolatilization stages increases and the venting zone pressure decreases, the devolatilization efficiency increases. Increasing the number of devolatilization stages increases equipment costs. Under specific operating conditions, decreasing the venting zone pressure increases process energy consumption and the risk of material overflow from the venting zone, compromising process stability. Furthermore, the novel dynamic single-screw devourer of the present invention maintains the advantage of low shear stress of the single-screw devourer while significantly increasing the devouring interface area and devouring efficiency through the arrangement of internal components in the diversion ring.

[0054] To simulate the material system in a polymerization reactor, in all embodiments of the present invention, a twin-screw extruder with a solvent injection system is installed at the feed section of the dynamic single-screw devolatilizer to achieve mixing and dissolution of polymer resin raw materials and solvent system in a certain proportion, so as to obtain a polymer solution with a certain temperature, pressure and solvent concentration as the raw material solution of the dynamic single-screw devolatilizer.

[0055] In this invention, polyolefin elastomer (POE) is primarily used as the devolatilization polymer. The selected POE melt index is 0.5 g / 10 min (2.16 kg / 10 min). A mixture of 1-octene and n-hexane is used as the solvent, with a mass ratio of 7:3. After exiting the dynamic single-screw devolatilizer, the polymer system passes through a start-up valve and enters an underwater pelletizing system to obtain POE particles. The volatile content in the POE particles is determined by headspace gas chromatography. Typical headspace sampler operating conditions are: vial temperature 190°C, equilibration time 20 min; circulation temperature 170°C, circulation time 25 min; quantitative loop temperature 160°C, quantitative loop time 0.15 min, quantitative loop equilibration time 0.02 min.

[0056] Example 1

[0057] In this embodiment, the dynamic single-screw exhaust device uses a screw with a diameter D = 58 mm and a length-to-diameter ratio L / D = 60. It features rear exhaust and a three-stage front exhaust. The feed section is 6.5D long. At the feed inlet, the screw lead is 1.0D, and the groove depth is 0.2D. The rear exhaust section is 5.5D long, with the same lead as the feed section (1.0D), and the groove depth gradually changes from 0.2D to 0.07D. The shell and screw configuration of the stripping section in the three-stage front exhaust are identical. The stripping section is 2D long and uses a slotted right-hand single-start thread. The damping ring has a diameter of 0.97D and a length of 9 mm. The three-stage forced diversion zone is 1.4D long. The first-stage forced diversion zone uses a multi-hole diversion ring with a hole diameter of 1.5 mm, a radial hole spacing of 1.8 mm, and an axial hole spacing of 6 mm. The second and third stage diversion zones employ slit diversion rings, with a slit width of 1mm, a length of 18mm, and a radial and axial slit spacing of 3mm. The forced diversion zone and exhaust zone below the devolatilization section use a 6-thread screw; the first stage has a length of 5D, and the second and third stages have lengths of 5.5D, with a lead of 3D. The screw speed is 200rpm. Downstream of the dynamic single-screw devolatilizer are sequentially installed an start-up valve and an underwater pelletizing system.

[0058] This embodiment uses a polyolefin elastomer (POE) system with a melt index of 0.5 g / 10 min (2.19 kg / 190°C), a 1-octene / n-hexane mixture as the solvent (mass ratio 7:3), a total yield of 60 kg / hr, and a solvent concentration of 8 wt%. The feed solution temperature is 220°C, and the shell temperature of the dynamic single-screw devourer is also 220°C. The operating pressure of the post-exhaust gas is 30 kPa. No stripping agent is injected before the first-stage exhaust zone, and the operating pressure of the first-stage exhaust zone is 30 kPa. Water is used as the stripping agent, and the injection rate of the second and third-stage stripping agents is 2 mL / min. The operating pressures at the exhaust ports are 1 kPa and 0.2 kPa, respectively.

[0059] The final concentration of 1-octene in the POE particles was 125 ppm, and the concentration of n-hexane was 15 ppm.

[0060] Example 2

[0061] In this embodiment, the dynamic single-screw exhaust device uses a screw with a diameter D = 58 mm and a length-to-diameter ratio L / D = 47. It features rear exhaust and two-stage front exhaust. The feed section is 5 D long. At the feed inlet, the screw lead is 0.8 D and the groove depth is 0.25 D. The rear exhaust section is 5 D long, with the same lead as the feed section (0.8 D), and the groove depth gradually changes from 0.25 D to 0.08 D. The shell and screw configuration of the two-stage front exhaust stripping section are identical. The stripping section is 2.5 D long and uses a slotted right-hand single-start thread. The damping ring has a diameter of 0.97 D and a length of 9 mm. The first-stage forced diversion zone is 1.4 D long and uses a multi-hole diversion ring with a hole diameter of 1.2 mm, a radial hole spacing of 2 mm, and an axial hole spacing of 4 mm. The second-stage forced flow divider has a length of 2D and uses a slit flow divider ring with a slit width of 1mm and a length of 16mm. The radial and axial slit spacing is 3mm. The forced flow divider zone and the area below the exhaust zone in the devolatilization section use a 6-thread screw. The first stage has a length of 5D, the second stage has a length of 6D, and the lead is 2.5D. The screw speed is 220rpm.

[0062] This embodiment uses a polyolefin elastomer (POE) system with a melt index of 5 g / 10 min (2.19 kg / 190°C). The solvent is a mixture of 1-octene and n-hexane in a mass ratio of 7:3, with a total yield of 80 kg / hr and a solvent concentration of 5 wt%. The temperature of the feed solution and the shell temperature of the dynamic single-screw devourer are both 200°C. The operating pressure of the exhaust gas is 10 kPa. Water is used as the stripping agent, with the injection rate of the first and second stage stripping agents at 3 mL / min. The operating pressures at the exhaust ports are 0.5 kPa and 0.2 kPa, respectively.

[0063] The final concentration of 1-octene in the POE particles was 65 ppm, and the concentration of n-hexane was 5 ppm.

[0064] Example 3

[0065] In this embodiment, the dynamic single-screw exhaust device uses a screw with a diameter D = 58 mm and a length-to-diameter ratio L / D = 60. It features rear exhaust and a three-stage front exhaust. The feed section is 10 D long. At the feed inlet, the screw lead is 2.0 D and the groove depth is 0.3 D. The rear exhaust section is 10.0 D long, with the same 1.5 D lead as the feed section, and the groove depth gradually changes from 0.3 D to 0.2 D. The shell and screw configuration of the stripping section in the three-stage front exhaust are identical. The stripping section is 5 D long and uses a slotted right-hand single-start thread. The damping ring has a diameter of 1.0 D and a length of 15 mm. The three-stage forced diversion zone is 5 D long. The first-stage forced diversion zone uses a multi-hole diversion ring with a hole diameter of 5 mm, a radial hole spacing of 6 mm, and an axial hole spacing of 10 mm. The second and third stage diversion zones employ slit diversion rings, with a slit width of 5mm and a length of 50mm, and both radial and axial slit spacing are 5mm. The forced diversion zone and exhaust zone below the devolatilization section use 20-start threads; the first stage has a length of 10D, and the second and third stages have lengths of 8D, with a lead of 8D. The screw speed is 300rpm. Downstream of the dynamic single-screw devolatilizer are sequentially installed an start-up valve and an underwater pelletizing system.

[0066] This embodiment uses a polyolefin elastomer (POE) system with a melt index of 0.5 g / 10 min (2.19 kg / 190°C), a 1-octene / n-hexane mixture as the solvent (mass ratio 7:3), a total yield of 50 kg / hr, and a solvent concentration of 5 wt%. The feed solution temperature is 230°C, and the shell temperature of the dynamic single-screw devourer is also 230°C. The operating pressure of the post-exhaust gas is 20 kPa. No stripping agent is injected before the first-stage exhaust zone, and the operating pressure of the first-stage exhaust zone is 5 kPa. Water is used as the stripping agent, and the injection rate of the second and third-stage stripping agents is 2 mL / min. The operating pressures at the exhaust ports are 1 kPa and 0.2 kPa, respectively.

[0067] The final concentration of 1-octene in the POE particles was 25 ppm, and the concentration of n-hexane was 8 ppm.

[0068] Example 4

[0069] In this embodiment, the dynamic single-screw exhaust device uses a screw with a diameter D = 58 mm and a length-to-diameter ratio L / D = 60. It features rear exhaust and a three-stage front exhaust. The feed section is 4 D long. At the feed inlet, the screw lead is 2.0 D and the groove depth is 0.15 D. The rear exhaust section is 4.0 D long, with the same lead as the feed section (0.5 D), and the groove depth gradually changes from 0.15 D to 0.05 D. The stripping section of the three-stage front exhaust has the same shell and screw configuration. The stripping section is 1.5 D long and uses a slotted right-hand single-start thread. The damping ring has a diameter of 0.9 D and a length of 6 mm. The three-stage forced diversion zone is 1 D long. The first-stage forced diversion zone uses a multi-hole diversion ring with a hole diameter of 1 mm, a radial hole spacing of 1 mm, and an axial hole spacing of 1 mm. The second and third stage diversion zones employ slit diversion rings, with a slit width of 1mm and a length of 10mm, and a radial and axial slit spacing of 1mm. The forced diversion zone and exhaust zone below the devolatilization section use a two-start thread; the first stage has a length of 4D, and the second and third stages have lengths of 5D, with a lead of 1.5D. The screw speed is 40rpm. Downstream of the dynamic single-screw devolatilizer are sequentially installed an start-up valve and an underwater pelletizing system.

[0070] This embodiment uses a polyolefin elastomer (POE) system with a melt flow rate of 0.5 g / 10 min (2.19 kg / 190°C). The solvent is a mixture of 1-octene and n-hexane at a mass ratio of 7:3, with a total yield of 55 kg / hr and a solvent concentration of 8 wt%. The temperature of the feed solution and the shell temperature of the dynamic single-screw devourer are both 230°C. The operating pressure of the post-exhaust gas is 26 kPa. No stripping agent is injected before the first-stage exhaust zone, and the operating pressure of the first-stage exhaust zone is 10 kPa. Water is used as the stripping agent, and the injection rate of the second and third-stage stripping agents is 2 mL / min. The operating pressures at the exhaust ports are 1 kPa and 0.2 kPa, respectively.

[0071] The final concentration of 1-octene in the POE particles was 165 ppm, and the concentration of n-hexane was 25 ppm.

[0072] In summary, the continuous dynamic high-efficiency devolatilization method of the present invention has the following advantages:

[0073] 1. A dynamic single-screw devolatilizer is used to devolatilize polymer solution raw materials with a volatile concentration of 5-10% to a volatile concentration of 10-200ppm;

[0074] 2. By designing a novel dynamic single-screw devourer screw-shell structure, the mass transfer interface of the single-screw devourer is significantly improved while retaining the advantage of low shear stress.

[0075] 3. Based on different target volatile concentrations, different polymer diversion internal components are designed. The target devolatification efficiency is achieved by adjusting the mass transfer interface area on the basis of a screw-shell system, effectively reducing the investment and maintenance costs of the equipment.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these should also be considered within the scope of protection of the invention.

Claims

1. A continuous, dynamic, and efficient devolatilization method for polymer / volatile fraction systems based on a high mass transfer interface, characterized in that, Includes the following steps: A single-screw dynamic devolatilizer is employed, which mainly consists of a rotating single screw and a housing. A polymer solution is added to the single-screw dynamic devolatilizer, the polymer solution comprising devolatilized polymer and volatile small molecules, the volatile small molecules including organic solvents, residual monomers, water, or reaction byproducts. The material in the devolatilization section is conveyed and compressed by the screw after devolatilization, and directly leaves the dynamic devolatilizer; or A side-feed extruder is set up downstream of the devolatilization section to add plastic additives into the polymer melt after devolatilization. The polymer is then melt-blended with the polymer at the end of the single-screw dynamic devolatilizer before leaving the dynamic devolatilizer.

2. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 1, characterized in that, The single-screw dynamic devourer is equipped with a drive motor and gearbox, a rear exhaust section, a feeding section, a first-stage stripping section, a first-stage devouring section, a second-stage stripping section, a third-stage stripping section, a third-stage devouring section, and a conveying / mixing section, arranged sequentially from the end to the front.

3. A continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface, as described in claim 2, is characterized in that... During the devolatilization process, the number of stages for post-venting devolatilization and pre-venting devolatilization is selected according to the devolatilization requirements. When the volatile content in the polymer solution entering the single-screw dynamic devolatilizer is 5-20% and still has flash evaporation potential, a post-venting stage is set to discharge the volatiles, and the feed stage collects the polymer. When the volatile content in the polymer solution entering the single-screw dynamic devolatilizer is ≤2%, it can be selected to directly enter the downstream first-stage stripping stage and first-stage devolatilization stage through the feed stage.

4. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 2, characterized in that, The length L3 of the feed section is 3-15D, preferably 6-8D; the screw at the feed inlet position is a single-start or multi-start deep groove thread with a lead of 0.5-4D, preferably 0.6-1.5D, more preferably 0.9-1.5D, and the groove depth is 0.05-0.4D, preferably 0.1-0.2D. The length L2 of the rear exhaust section is 3-15D, preferably 4-6D; it adopts a single-start or multi-start thread, the thread lead is 0.5-4D, preferably 0.9-1.5D, and the depth of the thread groove is 0.05-0.4D, preferably 0.08-0.20D. The depth of the thread groove gradually decreases or remains constant from the feed section to the reducer side. The temperature of the material entering the dynamic degassing device is higher than the boiling point of the volatiles, and the pressure is higher than the corresponding saturation pressure. The pressure of the rear exhaust section is 1-100 kPa, preferably 10-80 kPa, and more preferably 30-60 kPa.

5. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 4, characterized in that, After being concentrated by post-gas extraction, the solution is pressurized in the feed section and then enters the first-stage stripping zone. The stripping agent is selected from water, CO2, or N2. The injection amount of stripping agent upstream of each devolatilization section is 0-2 wt% M, preferably 0.2-1 wt% M, more preferably 0.2-0.5 wt% M. The length of the stripping section is 1.5-5 D, preferably 2-3 D. The screw of the stripping section is equipped with a mixing element, including a pin block or a slotted screw rib. The end of the stripping section is provided with a reverse spiral structure or a damping ring. The diameter of the damping ring is 0.9-1.0 D, preferably 0.96-0.99 D, and the width of the damping ring is 0.01-1 D, preferably 0.05-0.2 D.

6. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 5, characterized in that, The material flowing out of the stripping section enters the space formed by the diversion ring and its pressure block in the forced diversion zone of the shell of the devolatilization section, and then flows out into the screw groove of the screw; the length of the forced diversion zone is 0.1-5D, preferably 0.5-2D; The flow divider ring includes, but is not limited to, slit type and porous type. The slit width of the slit type flow divider ring is 0.1-5mm, preferably 0.5-2mm; the slit length is 10-200mm, preferably 20-80mm; the slit spacing is 1-10mm, preferably 2-3mm; the entrance of the slit is chamfered to avoid dead zones on the outer surface of the flow divider ring; the slits are aligned or staggered in the axial direction; the slits can be distributed in a straight line or a spiral in the axial direction. The end diameter of the porous flow divider ring is 0.2-10 mm, preferably 0.5-3 mm; the radial hole spacing is 1-10 mm, preferably 2-5 mm; the axial hole spacing is 1-10 mm, preferably 2-5 mm; and the inlet of the holes is chamfered. The holes can be distributed in a straight line or a spiral in the axial direction.

7. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 6, characterized in that, The screws in the forced diversion zone and exhaust zone of the devouring section are composed of multi-start equal-depth and equal-pitch threads with a length of 1-10D, preferably 5-8D; the thread lead is 1-10D, preferably 2-6D; the number of thread starts is 2-20, preferably 4-12; and the pressure in the exhaust zone is 0.1-80kPa, preferably 0.1-60kPa, more preferably 0.1-20kPa.

8. The continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 6, characterized in that, The screw in the rear section of the exhaust zone transports and compresses the devolatilized polymer melt, and after pressure is built up, it enters the next stage of stripping zone and devolatilization zone; The concentration of volatiles in the polymer melt after being devolatilized by the single-screw dynamic devolatilizer is 10-3000 ppm, preferably 100-400 ppm, more preferably 100-200 ppm; the rotational speed of the single screw is 10-300 rpm, preferably 40-200 rpm. The material output from the final stage of the devolatilization zone is conveyed and compressed by the screw, and then leaves the dynamic devolatilization unit directly.

9. A continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 6, characterized in that, The screw in the rear section of the exhaust zone transports and compresses the devolatilized polymer melt, and after pressure is built up, it enters the next stage of stripping zone and devolatilization zone; The concentration of volatiles in the polymer melt after being devolatilized by the single-screw dynamic devolatilizer is 10-3000 ppm, preferably 100-400 ppm, more preferably 100-200 ppm; the rotational speed of the single screw is 10-300 rpm, preferably 40-200 rpm. The material output from the final stage of the devolatilization zone is thoroughly mixed with the plastic additives from the side feed before leaving the dynamic devolatilization unit.

10. A continuous dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface according to claim 9, characterized in that, The plastic additives include antioxidants, UV stabilizers, lubricants, antistatic agents, and pigments.

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