Continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on high mass transfer interfaces

Abstract

This invention provides a continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on high mass transfer interfaces. [Solution] The method includes the steps of adding a polymer solution to a single-screw dynamic defoliation apparatus, wherein the polymer solution contains a defoliated polymer and volatile small molecule substances, the volatile small molecule substances containing an organic solvent, residual monomer, water, or reaction by-products, and after the material in the defoliation section is defoliated, it is conveyed and compressed by a screw and then removed from the single-screw dynamic defoliation apparatus, or providing a side-feed extruder downstream of the defoliation section, adding a plastic additive to the defoliated polymer molten body, melting and mixing it with the defoliated polymer molten body at the end of the single-screw dynamic defoliation apparatus, and then removing it from the dynamic defoliation apparatus.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer production and processing, and particularly relates to a continuous, dynamic and efficient devolatilization method for a polymer / volatile component system based on a high mass transfer interface.

Background Art

[0002] In the polymer synthesis process, most polymer systems coming out of the reactor contain low molecular weight components such as residual monomers, organic solvents, water, and reaction by-products, which are collectively referred to as volatile components. The content of these volatile components may reach several tens of percent. The process of removing the above volatile components from the polymer body is called devolatilization, which improves the degree of polymerization and performance of the polymer, recovers the remaining monomers and solvents, removes odors, and meets the requirements of health and environment. Depending on the application field of the polymer product, the concentration of the target volatile component in the devolatilization process may be several tens to several thousand ppm (parts per million), and the energy consumption of the devolatilization process is as high as over 60% in the polymer synthesis process. Therefore, efficient devolatilization is an important means to reduce the polymer production cost and improve the product quality.

[0003] When the volatile content in the polymer system is high and the viscosity is low, a large number of bubbles are rapidly formed in the system under low-pressure conditions. These bubbles expand due to mass transfer and aggregation in the liquid phase, resulting in flash defloration. Flash defloration has high heat transfer and mass transfer efficiency, and the process is mainly controlled by phase equilibrium. As the concentration of volatile components in the system decreases and the system viscosity increases, the polymer system undergoes defloration through processes such as bubble nucleation, growth, aggregation / combination, and rupture, resulting in foam defloration. Bubble nucleation and growth are control steps of the defloration rate and are mainly determined by the viscoelasticity and superheating of the system. As the concentration of volatile components decreases further, few or no new bubbles are generated, and defloration is controlled by molecular diffusion at the polymer-gas phase interface. Control of diffusion for defloration is usually performed under high vacuum conditions, and improving the mass transfer interface region between the polymer molten material and the gas phase, and promoting surface renewal are effective means of improving defloration efficiency. There are many types of devolatilization equipment used in industry. These can be broadly divided into static devolatilization equipment, which mainly handles low-viscosity systems without mechanical stirring, such as flash evaporators and drop strip devolatilization equipment, and dynamic rotary devolatilization equipment, such as thin-film evaporators and screw devolatilization equipment, which are equipped with rotor elements for conveying and mixing polymer systems and can handle high-viscosity polymer systems. Among these, screw devolatilization equipment has advantages such as stable conveyance, good heat conduction, uniform mixing, and a fast surface renewal rate. Furthermore, a single screw devolatilization equipment can effectively handle systems with viscosities that differ by several orders of magnitude, thus occupying a unique position in the field of devolatilization equipment.

[0004] Patent CN110746524B features a two-stage devolatilization system with an upper phase separation chamber and a lower distributor subunit to increase the phase boundary area for devolatilization and extend the residence time of the devolatilization process. However, static devolatilization equipment cannot process high-viscosity, low-volatile content polymer systems because it cannot immediately renew the surface. The residual volatile content of polymer / volatile component systems devolatilized by the static devolatilization equipment of this invention is high, several thousand ppm, which is higher than the required residual volatile content of polymers in most application fields. The double-screw dynamic devolatilization equipment of Patent EP2168743 and Patent US 2020 / 0215738 incorporates a kneading section to apply shear to the polymer molten material in the kneading element, branching the melt beam in the screw groove to create the mass transfer interface region required for devolatilization and promote surface renewal. However, high shear stress causes polymer degradation and color change, affecting the quality of polymer products and limiting their application fields. Furthermore, compared to single-screw dynamic devolatilization systems, double-screw dynamic devolatilization systems have a more complex structure, resulting in higher manufacturing and maintenance costs. There are also unavoidable problems when using conventional single-screw dynamic devolatilization systems, specifically the following:

[0005] 1. The mass transfer interface generated in a single-screw dynamic devolatilization apparatus is extremely small, which significantly restricts its devolatilization efficiency.

[0006] 2. In industrial practice, single-screw dynamic devolatilization units can only process polymer solution raw materials with a volatile content of approximately 1% or less, thus limiting their range of applications.

[0007] 3. When the actual devolatilization situation changes, in the case of a double-screw devolatilization device, the combination of screw elements in the building block can be adjusted to respond to the new situational demands, but this reduces the operational flexibility of the overall screw structure of a single-screw dynamic devolatilization device. [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on a high mass transfer interface, in order to solve one or more of the problems of the prior art described above. [Means for solving the problem]

[0009] The present invention provides a continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on a high mass transfer interface, A single-screw dynamic devolatilization apparatus is used, the devolatilization apparatus mainly consists of a rotating single screw and a shell, a polymer solution is added to the single-screw dynamic devolatilization apparatus, the polymer solution contains a devolatilized polymer and volatile small molecule substances, the volatile small molecule substances contain an organic solvent, residual monomer, water or reaction by-products, the material in the devolatilization section is conveyed and compressed by the screw and then removed from the single-screw dynamic devolatilization apparatus, or The procedure includes providing a side-feed extruder downstream of the defolaral section, adding a plastic additive to the defolaralized polymer melt, melting and mixing it with the defolaralized polymer melt at the end of the single-screw dynamic defolaralizer, and then moving away from the single-screw dynamic defolaralizer.

[0010] In some embodiments, the single-screw dynamic devolatilization device is provided with a drive motor and reduction gearbox, a rear exhaust section, a feed section, a first-stage stripping section, a first-stage devolatilization section, a second-stage stripping section, a second-stage devolatilization section, a third-stage stripping section, a third-stage devolatilization section, and a conveying and mixing section, in that order from end to tip.

[0011] Here, the rear exhaust section, the third-stage stripping section, and the third-stage evaporative section may be omitted depending on the requirements.

[0012] In some embodiments, the devolatilization process may be configured to select between rear exhaust devolatilization and front exhaust devolatilization stages in response to devolatilization requirements. When the polymer solution entering the single-screw dynamic devolatilizer has a volatile content of 5-20% and still possesses flash evaporation potential, a rear exhaust section may be provided to discharge the volatile content, while a feed section may be used to capture the concentrated polymer solution. Alternatively, when the polymer solution entering the single-screw dynamic devolatilizer has a volatile content of ≤2%, the system may be configured to proceed directly to the downstream first-stage stripping section and first-stage devolatilization section via the feed section.

[0013] In some embodiments, the length L3 of the feed section is 3 to 15D, preferably 6 to 8D, the screw at the feed port location is a single-row or multi-row deep groove screw, the pitch is 0.5 to 4D, preferably 0.6 to 1.5D, more preferably 0.9 to 1.5D, and the groove depth is 0.05 to 0.4D, preferably 0.1 to 0.2D. The length L2 of the rear exhaust section is 3 to 15D, preferably 4 to 6D, and single-row or multi-threaded screws are used, with a screw pitch of 0.5 to 4D, preferably 0.9 to 1.5D, a screw groove depth of 0.05 to 0.4D, preferably 0.08 to 0.20D, where the screw groove depth gradually decreases or remains constant from the feed section to the reduction box side, and the material entering the single-screw dynamic devolatilizer is at a temperature higher than the boiling point of the volatile components and at a pressure higher than the corresponding saturation pressure, with the rear exhaust section pressure being 1 to 100kPa, preferably 10 to 80kPa, more preferably 30 to 60kPa.

[0014] Here, D is the outer diameter of the screw.

[0015] In some embodiments, the concentrated polymer solution obtained by the rear exhaust section treatment is compressed in a feed section to build up pressure, then enters a first-stage stripping section, where the stripping agent is selected from water, N2, or CO2, the amount of stripping agent injected upstream of each stage defoliation 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 provided with a mixing element including a pin block or a slotted screw flight, the end of the stripping section is provided with an inverted helical 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.

[0016] Here, M is the mass flow rate (kg / hr) of the polymer melt processed by the defoliation device.

[0017] In some embodiments, the material flowing out from the stripping section enters a space consisting of a diversion ring and its pressure block within a forced diversion area in the shell of the devolatile section, and flows further out into the screw grooves, the length of which is 0.1 to 5D, preferably 0.5 to 2D. The flow diversion rings include, but are not limited to, slit-type and porous types. For slit-type flow diversion rings, the stitch width is 0.1 to 5 mm, preferably 0.5 to 2 mm; the stitch length is 10 to 200 mm, preferably 20 to 80 mm; and the stitch spacing is 1 to 10 mm, preferably 2 to 3 mm. The entrances to the slits are chamfered to avoid creating dead zones on the outer surface of the flow diversion ring. In the axial direction, the slits may be arranged in a line or staggered, and the slits may be distributed linearly or spirally in the axial direction.

[0018] The end pore diameter of the porous flow divider ring is 0.2 to 10 mm, preferably 0.5 to 3 mm; the pore spacing in the radial direction is 1 to 10 mm, preferably 2 to 5 mm; the pore spacing in the axial direction is 1 to 10 mm, preferably 2 to 5 mm; the pore entrances are chamfered; and the pores can be distributed linearly or spirally in the axial direction.

[0019] In some embodiments, the screws at the forced diversion and exhaust area locations of the devolatilization section consist of multiple rows of equally spaced screws of equal depth, with a length of 1 to 10D, preferably 5 to 8D, a screw pitch of 1 to 10D, preferably 2 to 6D, a number of screw rows of 2 to 20, preferably 4 to 12, and an exhaust area pressure of 0.1 to 80 kPa, preferably 0.1 to 60 kPa, more preferably 0.1 to 20 kPa.

[0020] In some embodiments, the single-screw dynamic devolatilization device further includes a forced diversion area between the feed section and the rear exhaust section, the forced diversion area comprising a space consisting of a diversion ring and its pressure block, the length of the forced diversion area being 0.1 to 5D, preferably 0.5 to 2D. The flow diversion rings include, but are not limited to, slit-type and porous types. For slit-type flow diversion rings, the stitch width is 0.1 to 5 mm, preferably 0.5 to 2 mm; the stitch length is 10 to 200 mm, preferably 20 to 80 mm; and the stitch spacing is 1 to 10 mm, preferably 2 to 3 mm. The entrances to the slits are chamfered to avoid creating dead zones on the outer surface of the flow diversion ring. In the axial direction, the slits may be arranged in a line or staggered, and the slits may be distributed linearly or spirally in the axial direction.

[0021] The end pore diameter of the porous flow-dividing ring is 0.2 - 10 mm, preferably 0.5 - 3 mm. The pore spacing in the radial direction is 1 - 10 mm, preferably 2 - 5 mm. The pore spacing in the axial direction is 1 - 10 mm, preferably 2 - 5 mm. The pore inlet is chamfered, and the pores can be distributed linearly or spirally in the axial direction.

[0022] In some embodiments, the screw at the rear of the exhaust area conveys and compresses the devolatilized polymer melt. After the pressure is built up, it enters the next-stage stripping section and devolatilization section. In the polymer melt devolatilized by the single-screw dynamic devolatilization device, the concentration of volatile components 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 last-stage devolatilization section is conveyed and compressed by the screw and then leaves the single-screw dynamic devolatilization device as it is.

[0023] In some embodiments, the screw at the rear of the exhaust area conveys and compresses the devolatilized polymer melt. After the pressure is built up, it enters the next-stage stripping section and devolatilization section. In the polymer melt devolatilized by the single-screw dynamic devolatilization device, the concentration of volatile components 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 last-stage devolatilization section is mixed well with the plastic additives from the side feed and then leaves the single-screw dynamic devolatilization device.

[0024] In some embodiments, the plastic additives include antioxidants, UV stabilizers, lubricants, antistatic agents, pigments, etc.

Advantages of the Invention

[0025] The present invention has the following beneficial effects.

[0026] 1. A single-screw dynamic devolatilization device is used to devolatilize a polymer solution raw material with a volatile matter concentration of 5-10% to a volatile matter concentration of 10-200 ppm.

[0027] 2. By designing the screw-shell structure of the new single-screw dynamic devolatilization device, on the premise of retaining the advantage of low shear stress of the single-screw devolatilization device, the mass transfer interface of the single-screw dynamic devolatilization device is greatly improved.

[0028] 3. According to different target volatile matter concentrations, different polymer shunt internal parts are designed, and on one set of screw-shell, the target devolatilization efficiency is realized by adjusting the mass transfer interface area, effectively reducing the investment in equipment and maintenance costs.

Brief Description of the Drawings

[0029] [Figure 1] Figure 1 is a schematic diagram of a single-screw dynamic devolatilization device. [Figure 2] Figure 2 is a schematic configuration diagram of the screw of the rear exhaust section. [Figure 3] Figure 3 is a schematic configuration diagram of the screw of the stripping section. [Figure 4] Figure 4 is a schematic configuration diagram of the devolatilization section shell. [Figure 5] Figure 5 is a schematic diagram of a porous shunt ring. [Figure 6A] Figure 6A is a schematic diagram of a slit-type shunt ring. [Figure 6B] Figure 6B is a schematic diagram of a left-handed slit-type shunt ring. [Figure 6C] Figure 6C is a schematic diagram of a right-handed slit-type shunt ring. [Figure 7]Figure 7 is a schematic diagram of the evaporative section multithreading configuration. [Explanation of Symbols]

[0030] 1. Drive motor and reduction gearbox 2. Rear exhaust section 3. Feed Section 4. First stage stripping section 5. First Stage De-de-emission Section 6. Second Stage: Stripping Section 7. Second Stage De-energization Section 8. Third Stage: Stripping Section 9. Third Stage De-emission Section 10 Conveying and Mixing Section [Modes for carrying out the invention]

[0031] The present invention will be described in more detail by the embodiment.

[0032] In this invention, a single-screw dynamic devolatilization apparatus is used. As shown in Figure 1, the single-screw dynamic devolatilization apparatus is provided with a rear exhaust section, a feed section, a first-stage forward exhaust area (including the first-stage stripping section and the first-stage devolatilization section), a second-stage forward exhaust area (including the second-stage stripping section and the second-stage devolatilization section), and a third-stage forward exhaust area (including the third-stage stripping section and the third-stage devolatilization section) in order from the end (drive motor / reduction box end) to the front (head end). The raw material for the single-screw dynamic devolatilization apparatus is derived from a polymer solution containing volatile components in a polymerization reactor. In this invention, the maximum solution concentration that the single-screw dynamic devolatilization apparatus can process is 20 wt%. To obtain ideal product performance, a side-feed extruder may be further provided downstream of the devolatilization section to add plastic additives (e.g., antioxidants, UV stabilizers, lubricants, antistatic agents, pigments, etc.) to the devolatilized polymer melt and melt-mix them together with the devolatilized polymer melt in the final section of the single-screw dynamic devolatilization apparatus. Granulation equipment is connected to the outlet end of the single-screw dynamic devolatilization unit, such as strand pelletizing or underwater pelletizing. One or more of the following are connected between the single-screw dynamic devolatilization unit and the granulation equipment: a screen changer, a melt pump, and a start valve.

[0033] In the specific devolatilization process, the stages of rear exhaust devolatilization and front exhaust devolatilization (first, second, or third stage) are selected according to the devolatilization requirements. In a polymer solution in a single-screw dynamic devolatilization apparatus, if the concentration of volatile components is high (5-20%) and still has flash evaporation potential, a rear exhaust section is provided to discharge the volatile components, and the feed section captures the concentrated polymer solution. On the other hand, if the concentration of volatile components in the polymer solution entering the single-screw dynamic devolatilization apparatus is very low (≤2%), it can proceed directly to the downstream first-stage stripping section and first-stage devolatilization section via the feed section. The length L3 of the feed section is 3-15D (where D is the screw diameter), preferably 6-8D. Here, the range D for a small dynamic devolatilization apparatus is 30-150mm, and the range D for a large dynamic devolatilization apparatus is 150-600mm. The screws at the feed port location are single-row or multi-row deep groove screws, with a pitch of approximately 0.5 to 4D, preferably 0.6 to 1.5D, more preferably 0.9 to 1.5D, and a groove depth of 0.05 to 0.4D, preferably 0.1 to 0.2D. As shown in Figure 1, a high-temperature, high-pressure polymer solution enters the single-screw dynamic defoliation unit, causing bubbles to vigorously grow at the feed location and immediately expand to fill all the grooves. The length L2 of the rear exhaust section is 3 to 15D, preferably 4 to 6D. Single-row or multi-thread screws are used, with a screw pitch of 0.5 to 4D, preferably 0.9 to 1.5D, and a groove depth of 0.05 to 0.4D, preferably 0.08 to 0.20D, where the groove depth gradually decreases from the feed section towards the reduction box side, or remains constant. As the screw groove depth gradually decreases, the bubbles burst, and the pressure difference separates the volatile gases, which are then discharged from the rear exhaust port. The viscous flow generated by the rotation of the screw carries the concentrated polymer solution downstream.The material entering the single-screw dynamic devolatilization unit is devolatilizable under conditions where the temperature is higher than the boiling point of the volatile component, the pressure is higher than the corresponding saturation pressure, and the rear exhaust is devolatilizable under normal or negative pressure conditions, with the rear exhaust section pressure being 1 to 100 kPa (absolute pressure), preferably 10 to 80 kPa, more preferably 30 to 60 kPa.

[0034] The polymer solution, concentrated by rear exhaust, is compressed in the feed section, and after pressure is built up, it enters the first-stage stripping section 4. The stripping agent is usually water, CO2, or N2, which can effectively reduce the partial pressure of volatiles in the gas phase, improve the driving force of devolatile mass transfer, generate bubbles, increase the gas-liquid mass transfer area, and enhance the devolatile process. The amount of stripping agent injected upstream of each stage devolatile section is 0-2 wt%M (where M is the mass flow rate of the polymer molten material processed by the devolatile apparatus in kg / hr), preferably 0.2-1 wt%M, more preferably 0.2-0.5 wt%M. Depending on the requirements of the devolatile process, the injection area of ​​the stripping agent may be selected, and the stripping agent may be injected before any of the first to third stage devolatile sections, or only before the last one or two stage devolatile sections. 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, which are then uniformly dispersed in the polymer solution. The rotation speed of the single screw is 10 to 300 rpm, preferably 60 to 200 rpm. Mixing elements such as pin blocks or slotted screw flights are provided on the screw of the stripping section. As shown in Figure 3, an inverted helical structure or damping ring is provided at the end of the stripping section. The diameter of the damping ring is 0.9 to 1.0D, preferably 0.96 to 0.99D. The width of the damping ring is 0.01 to 1D, preferably 0.05 to 0.2D.

[0035] Due to the barrier effect of the inverse helical structure or damping ring, as shown in Figure 4, the material flowing out from the stripping section cannot flow downstream along the screw, but instead enters the space through the diversion ring and its pressure block in the forced diversion area within the shell of the devolatilization section, and then flows out further into the screw threads. The diversion ring forcibly diverts the molten material, generating a large surface area of ​​the molten material and providing a gas-liquid phase interface for devolatilization. The phase interface created by forced diversion is constantly renewed, significantly improving the devolatilization efficiency of the single-screw dynamic devolatilization apparatus. The length of the forced diversion area is 0.1 to 5D, preferably 0.5 to 2D. Typical diversion rings include, but are not limited to, slit-type and porous types, as shown in Figures 5 and 6. The stitch width of the slit-type diversion ring is 0.1 to 5 mm, preferably 0.5 to 2 mm. The stitch length is 10 to 200 mm, preferably 20 to 80 mm. The spacing between stitches (including in the axial and radial directions) is 1 to 10 mm, preferably 2 to 3 mm. The entrances to the slits are chamfered to avoid the formation of dead zones on the outer surface of the flow diversion ring. In the axial direction, the slits may be arranged in a single line or staggered. The slits can be distributed linearly or spirally in the axial direction. The end pore diameter of the porous flow diversion ring is 0.2 to 10 mm, preferably 0.5 to 3 mm. The pore spacing in the radial direction is 1 to 10 mm, preferably 2 to 5 mm. The pore spacing in the axial direction is 1 to 10 mm, preferably 2 to 5 mm. The entrances to the pores are chamfered. The pores can be distributed linearly or spirally in the axial direction.

[0036] The screws in the forced diversion and exhaust areas of the devolatilization section consist of multiple rows of equally spaced screws of equal depth, with a length of 1 to 10D, preferably 5 to 8D, as shown in Figure 7. The screw pitch is 1 to 10D, preferably 2 to 6D. The number of screw rows is 2 to 20, preferably 4 to 12. The number of screw rows is defined as the number of threads in the cross-section of the screw and is the most important screw parameter affecting the control of diffusion for devolatilization. As the number of screw rows increases, the diversion of the melt beam in the screw grooves increases the interface area of ​​the molten film and promotes the surface renewal rate of the molten film. As the screw diameter decreases, increasing the number of screw rows significantly improves the difficulty of processing. The pressure (absolute pressure) in the exhaust area is 0.1 to 80 kPa, preferably 0.1 to 60 kPa, more preferably 0.1 to 20 kPa. As the volatile content in the raw material solution decreases or as defloration progresses, the operating pressure in the exhaust area gradually decreases, improving defloration efficiency. The volatile content in the polymer melt deflored by the single-screw dynamic defloration apparatus is 10 to 3000 ppm, determined by factors such as the volatile content in the raw material solution, defloration, and the performance requirements of the target product, and is preferably 100 to 400 ppm, more preferably 100 to 200 ppm.

[0037] The screw at the rear of the exhaust area transports and compresses the defolable polymer molten material, and after pressure is built up, it enters the next stage, the stripping section, then the defolation section. The shell, screw configuration, and process conditions of each stage of the stripping and defolation sections may be exactly the same, or they may be adjusted accordingly as defolation progresses and the volatile content in the polymer molten material decreases. The material output from the final stage defolation section is transported and compressed by the screw and may be released directly from the single-screw dynamic defolation unit, or it may be thoroughly mixed with processing aids from the side feed, such as antioxidants, UV stabilizers, lubricants, antistatic agents, and pigments, before being released from the single-screw dynamic defolation unit.

[0038] By selecting different types and sizes of internal components in the flow divider ring depending on the properties of the polymer to be processed, such as rheological properties, and the volatile content in the raw material solution entering the devolatilization unit, the devolatilization efficiency of the single-screw dynamic devolatilization unit can be adjusted, and the operational flexibility of the single-screw dynamic devolatilization unit can be improved. Compared to conventional single-screw devolatilization units, the rear exhaust section according to the present invention can significantly increase the volatile content in the polymer solution entering the single-screw dynamic devolatilization unit, up to a maximum of 20 wt%. When the volatile content in the raw material entering the single-screw dynamic devolatilization unit is low, a rear exhaust section may not be necessary. When selecting the devolatilization stages and the operating pressures of the pre- and post- and post-exhaust areas, it is necessary to comprehensively consider factors such as equipment and process costs and process stability. Devolatilization efficiency improves with an increase in the number of devolatilization stages and a decrease in exhaust area pressure. However, increasing the number of devolatilization stages increases equipment costs. Under certain conditions, a decrease in exhaust area pressure increases process energy consumption and increases the risk of exhaust area leakage, impairing process stability. Furthermore, the novel single-screw dynamic devolatilization apparatus according to the present invention retains the advantage of low shear stress of a single-screw devolatilization apparatus while significantly improving the devolatilization interface region and devolatilization efficiency by installing components inside the flow divider ring.

[0039] To simulate the material system in the polymerization reactor, in all embodiments of the present invention, a double-screw extruder equipped with a solvent injection system is provided in the feed section of the single-screw dynamic defoliation apparatus, and the polymer resin raw material and the solvent system are mixed and dissolved in a constant ratio to obtain a polymer solution at a constant temperature, pressure, and solvent concentration as the raw material solution for the single-screw dynamic defoliation apparatus.

[0040] In the embodiments of the present invention, polyolefin elastomer POE is mainly used as the defoliation polymer, and the selected POE melt indices are 0.5 and 5 g / 10 min (2.16 kg / 10 min). A 1-octene / n-hexane mixture is used as the solvent, with a mass ratio of 7:3. After the polymer melt exits the single-screw dynamic defoliation apparatus, it enters an underwater pelletizing system through a start valve to produce POE particles. The volatile content of the POE particles is measured by headspace gas chromatography. Typical headspace sampler operating conditions are a vial temperature of 190°C, a balance time of 20 min, a circulation temperature of 170°C, a circulation time of 25 min, a quantitative loop temperature of 160°C, a quantitative loop time of 0.15 min, and a quantitative loop balance time of 0.02 min.

[0041] Example 1 The single-screw dynamic devolatar used in this embodiment has a screw diameter of D=58mm and an aspect ratio of L / D=60, and is equipped with rear exhaust and third-stage forward exhaust. The length of the feed section is 6.5D. The screw pitch at the feed port position is 1.0D, and the screw groove depth is 0.2D. The length of the rear exhaust section is 5.5D, the pitch is the same as the feed section at 1.0D, and the screw groove depth gradually changes from 0.2D to 0.07D. The shell and screw configuration of the stripping section of the third-stage forward exhaust is the same. The length of the stripping section is 2D, and a right-hand single-row screw with slots is used. The damping ring has a diameter of 0.97D and a length of 9mm. The length of the third-stage forced diversion area is 1.4D. The first-stage forced diversion area uses a porous diversion ring with a hole diameter of 1.5mm, a radial hole spacing of 1.8mm, and an axial hole spacing of 6mm. The second and third stage diversion areas use slit diversion rings with a narrow stitch width of 1 mm, a length of 18 mm, and a stitch spacing of 3 mm in both the radial and axial directions. Below the forced diversion and exhaust areas of the devolatilization section, six rows of screws are used, with the length of the first stage devolatilization section being 5D, the length of the second and third stage devolatilization sections being 5.5D, and the pitch being 3D. The screw rotation speed is 200 rpm. Downstream of the single-screw dynamic devolatilization device, a start valve and an underwater pelletizing system are installed in that order.

[0042] In this example, a polyolefin elastomer POE system was used, with a melt index of 0.5 g / 10 min (2.19 kg / 190°C), a solvent of 1-octene / n-hexane mixture with a mass ratio of 7:3, a total production of 60 kg / hr, and a solvent concentration of 8 wt%. The temperature of the raw material solution was 220°C, and the shell temperature of the single-screw dynamic devolatilization unit was 220°C. The operating pressure for rear exhaust was 30 kPa, no stripping agent was injected before the first-stage forward exhaust area, and the operating pressure for the first-stage forward exhaust area was 30 kPa. Water was used as the stripping agent, and the injection rate of the stripping agent into the second-stage forward exhaust area and the third-stage forward exhaust area was 2 mL / min, with the operating pressures of the exhaust ports being 1 kPa and 0.2 kPa, respectively. Ultimately, in the POE particles, the concentration of 1-octene was 125 ppm, and the concentration of n-hexane was 15 ppm.

[0043] Example 2 The single-screw dynamic devolatar used in this embodiment has a screw diameter of D=58mm and an aspect ratio of L / D=47, and is equipped with rear exhaust and second-stage forward exhaust. The length of the feed section is 5D. The screw pitch at the feed port position is 0.8D, and the screw groove depth is 0.25D. The length of the rear exhaust section is 5D, the pitch is the same as the feed section at 0.8D, and the screw groove depth gradually changes from 0.25D to 0.08D. The shell and screw configuration of the stripping section of the second-stage forward exhaust is the same. The length of the stripping section is 2.5D, and a right-hand single-row screw with slots is used. The damping ring has a diameter of 0.97D and a length of 9mm. The length of the first-stage forced diversion area is 1.4D, and the first-stage forced diversion area uses a porous diversion ring with a hole diameter of 1.2mm, a radial hole spacing of 2mm, and an axial hole spacing of 4mm. The length of the second-stage forced diversion area is 2D, and a slit diversion ring is used with a narrow stitch width of 1 mm, a length of 16 mm, and a stitch spacing of 3 mm in both the radial and axial directions. Below the forced diversion and exhaust areas of the evaporative section, six rows of screws are used, with a first-stage length of 5D, a second-stage length of 6D, and a pitch of 2.5D. The screw rotation speed is 220 rpm.

[0044] In this example, a polyolefin elastomer POE system was used, with a melt index of 5 g / 10 min (2.19 kg / 190°C), a solvent of 1-octene / n-hexane mixture with a mass ratio of 7:3, a total production of 80 kg / hr, and a solvent concentration of 5 wt%. The temperature of the raw material solution was 200°C, and the shell temperature of the single-screw dynamic devolatilization unit was 200°C. The operating pressure for rear exhaust was 10 kPa, water was used as the stripping agent, the injection rate of the stripping agent in the first-stage forward exhaust area and the second-stage forward exhaust area was 3 mL / min, and the operating pressures of the exhaust ports were 0.5 kPa and 0.2 kPa, respectively.

[0045] Ultimately, in the POE particles, the concentration of 1-octene was 65 ppm, and the concentration of n-hexane was 5 ppm.

[0046] Example 3 The single-screw dynamic devolatar used in this embodiment has a screw diameter of D=58mm and an aspect ratio of L / D=60, and is equipped with rear exhaust and third-stage forward exhaust. The length of the feed section is 10D. The screw pitch at the feed port position is 2.0D, and the screw groove depth is 0.3D. The length of the rear exhaust section is 10.0D, the pitch is the same as the feed section at 1.5D, and the screw groove depth gradually changes from 0.3D to 0.2D. The shell and screw configuration of the stripping section of the third-stage forward exhaust is the same. The length of the stripping section is 5D, and a right-hand single-row screw with slots is used. The damping ring has a diameter of 1.0D and a length of 15mm. The length of the third-stage forced diversion area is 5D. The first-stage forced diversion area uses a porous diversion ring with a hole diameter of 5mm, a radial hole spacing of 6mm, and an axial hole spacing of 10mm. The second and third stage diversion areas use slit diversion rings with a narrow stitch width of 5 mm, a length of 50 mm, and a stitch spacing of 5 mm in both the radial and axial directions. Below the forced diversion and exhaust areas of the devolatilization section, 20 rows of screws are used, with a length of 10D for the first stage, and a length of 8D for the second and third stages, and a pitch of 8D. The screw rotation speed is 300 rpm. Downstream of the single-screw dynamic devolatilization device, a start valve and an underwater pelletizing system are installed in order.

[0047] In this example, a polyolefin elastomer (POE) system was used, with a melt index of 0.5 g / 10 min (2.19 kg / 190°C), a solvent of 1-octene / n-hexane mixture with a mass ratio of 7:3, a total production of 50 kg / hr, and a solvent concentration of 5 wt%. The temperature of the raw material solution was 230°C, and the shell temperature of the single-screw dynamic devolatilization unit was 230°C. The operating pressure for rear exhaust was 20 kPa, no stripping agent was injected before the first-stage forward exhaust area, and the operating pressure for the first-stage forward exhaust area was 5 kPa. Water was used as the stripping agent, and the injection rate of the stripping agent into the second-stage forward exhaust area and the third-stage forward exhaust area was 2 mL / min, with the operating pressures of the exhaust ports being 1 kPa and 0.2 kPa, respectively. Ultimately, in the POE particles, the concentration of 1-octene was 25 ppm, and the concentration of n-hexane was 8 ppm.

[0048] Example 4 The single-screw dynamic devolatar used in this embodiment has a screw diameter of D=58mm and an aspect ratio of L / D=60, and is equipped with rear exhaust and third-stage forward exhaust. The length of the feed section is 4D. The screw pitch at the feed port position is 2.0D, and the screw groove depth is 0.15D. The length of the rear exhaust section is 4.0D, the pitch is the same as the feed section at 0.5D, and the screw groove depth gradually changes from 0.15D to 0.05D. The shell and screw configuration of the stripping section of the third-stage forward exhaust is the same. The length of the stripping section is 1.5D, and a right-hand single-row screw with slots is used. The damping ring has a diameter of 0.9D and a length of 6mm. The length of the third-stage forced diversion area is 1D. The first-stage forced diversion area uses a porous diversion ring with a hole diameter of 1mm, a radial hole spacing of 1mm, and an axial hole spacing of 1mm. The second and third stage diversion areas use slit diversion rings with a narrow stitch width of 1 mm, a length of 10 mm, and a stitch spacing of 1 mm in both the radial and axial directions. Below the forced diversion and exhaust areas of the devolatilization section, two rows of screws are used, with a length of 4D for the first stage, and a length of 5D for the second and third stages, and a pitch of 1.5D. The screw rotation speed is 40 rpm. Downstream of the single-screw dynamic devolatilization device, a start valve and an underwater pelletizing system are installed in that order.

[0049] In this example, a polyolefin elastomer (POE) system was used, with a melt index of 0.5 g / 10 min (2.19 kg / 190°C), a solvent of 1-octene / n-hexane mixture with a mass ratio of 7:3, a total production of 55 kg / hr, and a solvent concentration of 8 wt%. The temperature of the raw material solution was 230°C, and the shell temperature of the single-screw dynamic devolatilization unit was 230°C. The operating pressure for rear exhaust was 26 kPa, no stripping agent was injected before the first-stage forward exhaust area, and the operating pressure for the first-stage forward exhaust area was 10 kPa. Water was used as the stripping agent, and the injection rate of the stripping agent into the second-stage forward exhaust area and the third-stage forward exhaust area was 2 mL / min, with the operating pressures of the exhaust ports being 1 kPa and 0.2 kPa, respectively. Ultimately, in the POE particles, the concentration of 1-octene was 165 ppm, and the concentration of n-hexane was 25 ppm.

[0050] In short, the continuous, dynamic, and efficient devolatilization method of the present invention has the following advantages.

[0051] 1. A single-screw dynamic defoliation apparatus is used to defoliate a polymer solution raw material with a volatile content of 5-10% to a volatile content of 10-200 ppm.

[0052] 2. By designing a new screw-shell structure for a single-screw dynamic devolatorial apparatus, the mass transfer interface of the single-screw devolatorial apparatus is significantly improved while retaining the advantage of low shear stress.

[0053] 3. By designing different polymer flow shunt components according to different target volatile content concentrations and adjusting the mass transfer interface region on a single screw-shell set, target defoliation efficiency is achieved, effectively reducing equipment investment and maintenance costs.

[0054] The above description is merely a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make several modifications and improvements without departing from the creative spirit of the present invention, and these are also considered to be within the scope of protection of the present invention.

Claims

1. A continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on a high mass transfer interface, A single-screw dynamic devolatilization apparatus is used, the devolatilization apparatus mainly consists of a rotating single screw and a shell, a polymer solution is added to the single-screw dynamic devolatilization apparatus, the polymer solution contains a devolatilized polymer and volatile small molecule substances, the volatile small molecule substances contain an organic solvent, residual monomer, water or reaction by-products, the material in the devolatilization section is transported and compressed by the screw after devolatilization and then removed from the single-screw dynamic devolatilization apparatus, or The process includes the steps of installing a side-feed extruder downstream of the devolatilization section, adding plastic additives to the devolatilized polymer melt, melting and mixing them with the devolatilized polymer melt at the end of the single-screw dynamic devolatilization apparatus, and then moving away from the single-screw dynamic devolatilization apparatus. A continuous, dynamic, and efficient defloration method for polymer / volatile component systems based on a high mass transfer interface, characterized by the features described above.

2. The single-screw dynamic devolatilization device is provided with, in order from the end to the tip, a drive motor and reduction gearbox, a rear exhaust section, a feed section, a first-stage stripping section, a first-stage devolatilization section, a second-stage stripping section, a second-stage devolatilization section, a third-stage stripping section, a third-stage devolatilization section, and a conveying and mixing section. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 1.

3. In the devolatilization process, the stages of rear exhaust devolatilization and front exhaust devolatilization can be selected according to the devolatilization requirements. When the polymer solution in the single-screw dynamic devolatilizer has a volatile content of 5-20% and still has flash evaporation potential, a rear exhaust section is provided to discharge the volatile content, and a feed section captures the concentrated polymer solution. Alternatively, when the polymer solution in the single-screw dynamic devolatilizer has a volatile content of ≤2%, the feed section may be used to allow the solution to proceed directly to the downstream first-stage stripping section and first-stage devolatilization section. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 2.

4. The length L3 of the feed section is 3 to 15D, preferably 6 to 8D, the screws at the feed port location are single-row or multi-row deep groove screws, the pitch is 0.5 to 4D, preferably 0.6 to 1.5D, more preferably 0.9 to 1.5D, and the groove depth is 0.05 to 0.4D, preferably 0.1 to 0.2D. The length L2 of the rear exhaust section is 3 to 15D, preferably 4 to 6D, and single-row or multi-threaded screws are used, with a screw pitch of 0.5 to 4D, preferably 0.9 to 1.5D, a screw groove depth of 0.05 to 0.4D, preferably 0.08 to 0.20D, where the screw groove depth gradually decreases or remains constant from the feed section to the reduction box side, and the material entering the single-screw dynamic devolatilizer is at a temperature higher than the boiling point of the volatile components and at a pressure higher than the corresponding saturation pressure, with the rear exhaust section pressure being 1 to 100 kPa, preferably 10 to 80 kPa, more preferably 30 to 60 kPa. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 2.

5. The concentrated polymer solution obtained by the rear exhaust section treatment is compressed in the feed section to build pressure, then enters the first stage stripping section, where the stripping agent is water, CO2 ２ or N ２ The amount of stripping agent injected upstream of each stage of the devolatilization section is selected from the above, and the amount of stripping agent injected upstream of each stage of the devolatilization section is 0 to 2 wt% M, preferably 0.2 to 1 wt% M, more preferably 0.2 to 0.5 wt% M, the length of the stripping section is 1.5 to 5 D, preferably 2 to 3 D, the screw of the stripping section is provided with a mixed element including a pin block or a slotted screw flight, the end of the stripping section is provided with an inverted helical structure or a damping ring, the diameter of the damping ring is 0.9 to 1.0 D, preferably 0.96 to 0.99 D, and the width of the damping ring is 0.01 to 1 D, preferably 0.05 to 0.2 D. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 4.

6. The material flowing out from the stripping section enters the space formed by the diversion ring and its pressure block within the forced diversion area in the shell of the devolatile section, and then flows out further into the screw grooves. The length of the forced diversion area is 0.1 to 5D, preferably 0.5 to 2D. The flow diversion rings include, but are not limited to, slit-type and porous types. For slit-type flow diversion rings, the stitch width is 0.1 to 5 mm, preferably 0.5 to 2 mm; the stitch length is 10 to 200 mm, preferably 20 to 80 mm; the stitch spacing is 1 to 10 mm, preferably 2 to 3 mm; the slit entrances are chamfered to avoid dead zones on the outer surface of the flow diversion ring; the slits can be arranged in a single line or staggered in the axial direction; and the slits can be distributed linearly or spirally in the axial direction. The end pore diameter of the porous flow divider ring is 0.2 to 10 mm, preferably 0.5 to 3 mm; the pore spacing in the radial direction is 1 to 10 mm, preferably 2 to 5 mm; the pore spacing in the axial direction is 1 to 10 mm, preferably 2 to 5 mm; the pore entrances are chamfered; and the pores can be distributed linearly or spirally in the axial direction. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 5.

7. The screws in the forced diversion area and exhaust area of ​​the evaporative section consist of multiple rows of equally spaced screws of equal depth, with a length of 1 to 10D, preferably 5 to 8D, a screw pitch of 1 to 10D, preferably 2 to 6D, a number of screw rows of 2 to 20, preferably 4 to 12, and a pressure in the exhaust area of ​​0.1 to 80 kPa, preferably 0.1 to 60 kPa, more preferably 0.1 to 20 kPa. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 6.

8. The screw at the rear of the exhaust area transports and compresses the defolatant polymer molten material, and after pressure is built up, it enters the next stage, the stripping section, then the defolatant section. In a polymer molten material devolated by a single-screw dynamic devolatulator, the concentration of volatile components is 10 to 3000 ppm, preferably 100 to 400 ppm, more preferably 100 to 200 ppm, and the rotational speed of the single screw is 10 to 300 rpm, preferably 40 to 200 rpm. The material output from the final devolatilization section is transported and compressed by a screw and then released from the single-screw dynamic devolatilization unit. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 6.

9. The screw at the rear of the exhaust area transports and compresses the defolatant polymer molten material, and after pressure is built up, it enters the next stage, the stripping section, then the defolatant section. In a polymer molten material devolated by a single-screw dynamic devolatulator, the concentration of volatile components is 10 to 3000 ppm, preferably 100 to 400 ppm, more preferably 100 to 200 ppm, and the rotational speed of the single screw is 10 to 300 rpm, preferably 40 to 200 rpm. The material output from the final devolatilization section is thoroughly mixed with plastic additives from the side feed before being removed from the single-screw dynamic devolatilization unit. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 6.

10. The aforementioned plastic additive includes antioxidants, UV stabilizers, lubricants, antistatic agents, and pigments. A continuous, dynamic, and efficient defloration method for a polymer / volatile component system based on a high mass transfer interface as described in feature 9.

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