A system and process for devolatilization separation of polymer solutions

Abstract

The present invention relates to a system for devolatilization separation of polymer solutions, comprising: a pretreatment unit (1); a heater (2); a solvent devolatilizer (3); a dispersion mixer (4); a settling tank (5); a filtration unit; and a washing unit. The present application also discloses a process for devolatilization separation of polymer solutions using the above system. Compared with the prior art, the present application can reduce the temperature of flash devolatilization, simplify the "devolatilization + extrusion" process of polymer solutions, and can conveniently, efficiently and continuously obtain polymer particles with high purity.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a system and process for devolatilization separation of polymer solutions. Background Art

[0002] In common industrial process devices of solution polymerization method, for polymer homogeneous solutions, the most common devolatilization method is to heat and evaporate the solution. Since the molecular weights of polymers and solvents are very different, polymers will produce a swelling effect in solvents. High-concentration polymer solutions have high viscosities and extremely poor fluidity, resulting in difficulties in heat conduction and mass transfer. Therefore, the higher the polymer concentration, the more difficult the separation. If the separation requirements are to be met, the devolatilization temperature is often very high. However, even when heated to a very high temperature (usually above 200 °C), there will still be some solvents that are not evaporated (usually containing about 8-15% wt), and further removal of the solvents is required in a vacuum extruder at a higher temperature and under a vacuum state. To achieve a higher temperature, a high-temperature heat transfer medium system needs to be added. However, as the devolatilization temperature increases, polymers are prone to carbonization and oxidation discoloration, affecting the light transmittance of polymers; at the same time, high temperatures are likely to cause polymer depolymerization, generating small molecules and affecting the mechanical properties of polymers; moreover, the increase in operating temperature also raises the requirements for the materials of equipment and pipelines, increasing the project cost, and there are safety hazards in the long-term operation of equipment at high temperatures. To achieve a vacuum state, a vacuum system needs to be added. The vacuum system has high energy consumption, high mechanical failure rates, high requirements for the leakage of equipment pipelines, and great operation difficulties.

[0003] In the above devolatilization method, in order to overcome the problems of the fluidity of polymers during devolatilization and the more difficult separation with higher polymer concentrations, a "devolatilization + extrusion" process is often adopted, that is, multi-stage heating and then flashing (usually three-stage heating + three-stage flashing) are required, and finally the solvents are removed in a vacuum extruder to meet the product requirements. In view of this process, the devolatilization process is complex, the energy consumption required for devolatilization is high, and the key is that polymer devolatilization technology is in the hands of a few foreign technology holders with patents. Due to the particularity of polymer melts, there is only one supplier for key devolatilization equipment and vacuum extruders, resulting in expensive equipment and long equipment production cycles. At the same time, the contents of additives, residual monomers and solvents in polymer products are relatively high, affecting the product quality and performance, and it is very difficult to produce optical-grade polymers.

[0004] In common suspension polymerization industrial process equipment, the most common process flow is that under strong mechanical stirring or oscillation, the monomer is dispersed into droplets, suspended in water, and the polymerization reaction is initiated by an oil-soluble initiator. The specific process is generally to add dispersant and water into a reactor equipped with a high-speed stirrer, stir and disperse for 1.5 hours, then add monomers dissolved in initiator, control the reaction temperature according to a certain heating curve, and react for 3 hours. The polymer slurry from the reaction unit is centrifuged, washed, dried, and screened to obtain polymer particles.

[0005] The above process is industrially operated in an intermittent manner. In order to facilitate the separation and precipitation of the polymer, a dispersant needs to be added, resulting in a high content of dispersant and residual monomers in the product, affecting product quality and performance; a large amount of sewage is generated, polluting the environment and increasing treatment costs.

[0006] In addition, ionic liquids refer to substances that are liquid at room temperature or close to room temperature. They are generally composed of organic cations containing nitrogen and phosphorus and inorganic anions. They are also called room temperature molten salts, and their melting point is generally <100°C. Summary of the invention

[0007] The first technical problem to be solved by the present invention is to provide a system for devolatilization separation of polymer solutions in view of the current status of the prior art, so as to reduce the temperature of flash devolatilization and simplify the "devolatilization + extrusion" process of the polymer solution.

[0008] The second technical problem to be solved by the present invention is to provide a process for devolatilizing and separating the polymer solution using the above system, so as to obtain high-purity polymer particles conveniently, efficiently and continuously.

[0009] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a system for devolatilization and separation of polymer solution, characterized by comprising:

[0010] A pretreatment unit, used for heating the polymer solution, and having a solution inlet for inputting the polymer solution and a solution outlet for outputting the polymer solution;

[0011] A heater, used to heat and reduce the pressure of a mixed solution consisting of a polymer solution and an ionic liquid, and having a heating inlet for inputting the mixed solution and a heating outlet for outputting the mixed solution, wherein the heating inlet is connected to the solution outlet of the pretreatment unit through a first pipeline, and the first pipeline is connected to a second pipeline for conveying the ionic liquid;

[0012] A solvent devolatilizer, used to reduce the pressure of the heated mixed liquid to a slightly positive pressure state to evaporate the solvent, and comprising a devolatilization inlet connected to the heating outlet of the heater, a devolatilization outlet for the flash gas to be desorbed, and a fluid outlet;

[0013] A dispersion mixer is used to precipitate polymer powder and has a mixed liquid inlet connected to the fluid outlet of the above solvent devolatilizer, an ionic liquid inlet for inputting ionic liquid, and a fluid outlet.

[0014] A settling tank is used to perform settling separation on polymer and ionic liquid and has a separation inlet connected to the fluid outlet of the above dispersion mixer, a first separation outlet for outputting the separated ionic liquid, and a second separation outlet for outputting the separated polymer with liquid phase.

[0015] A filtering unit is used to filter out the residual liquid phase in the above separated polymer and has a filtering inlet connected to the second separation outlet of the above settling tank and a first filtering outlet for outputting the filtered polymer.

[0016] A washing unit has a washing inlet and a washing outlet. Its washing inlet is connected to the first filtering outlet of the above filtering unit, and its washing outlet is used to output the washed polymer, thereby obtaining the polymer after devolatilization and separation.

[0017] In this application, the solvent devolatilizer is prior art and is a stirrer type of at least one of ribbon type, twin-screw rotary type, pitched blade type, anchor type, and disk turbine type. Preferably, the heat tracing type of the solvent devolatilizer is an outer jacket, and the jacket type is at least one of spiral baffle type, semi-pipe spiral type, and hollow jacket type. The medium in the heat tracing pipe of the solvent devolatilizer is preferably at least one of steam, heat transfer oil, cooling water, and temperature-controlled water.

[0018] Preferably, it further includes a heat exchanger having a cold medium channel and a hot medium channel. The fluid outlet of the solvent devolatilizer is connected to the mixed liquid inlet of the dispersion mixer through the above hot medium channel. The inlet and outlet of the cold medium channel are both connected to the above pretreatment unit through their respective pipelines and are used to heat the polymer solution in the pretreatment unit. In addition, the heat exchanger can also directly select a cooler to cool the fluid output from the fluid outlet of the solvent devolatilizer.

[0019] Preferably, the washing unit further has an inlet for inputting ionic liquid. In this way, ionic liquid can be used to wash the polymer.

[0020] Preferably, the filtering unit further has a second filtering outlet for outputting the filtered liquid phase.

[0021] The washing unit further has an impurity fluid outlet for outputting the washed fluid with ionic liquid and impurities.

[0022] The system further includes an ionic liquid recovery unit, which has a recovery inlet communicating with the second filtration outlet and the impurity fluid outlet described above, a chemical reagent inlet for a chemical reagent capable of chemically reacting with the above impurities to enter, an inert gas inlet for an inert gas to enter, a recovery outlet for outputting the ionic liquid from which impurities have been removed, and an impurity outlet for outputting the reacted impurities. The recovery outlet communicates with the second pipeline, the ionic liquid feed inlet of the dispersion mixer, and the input port of the washing unit.

[0023] Further, the system further includes an ionic liquid intermediate tank. The recovery outlet of the ionic liquid recovery unit communicates with the second pipeline, the ionic liquid feed inlet of the dispersion mixer, and the input port of the washing unit through the ionic liquid intermediate tank; and the ionic liquid intermediate tank communicates with the first separation outlet of the settling tank.

[0024] The technical solution adopted by the present invention to solve the above second technical problem is as follows: A process for devolatilization separation of a polymer solution using the system as described above, characterized in that the steps are as follows:

[0025] First, the polymer solution coming from the reaction unit enters the pretreatment unit for heating and evaporation to obtain a first material stream, and the first material stream is a polymer homogeneous solution with a concentration of 10 - 50 wt%.

[0026] Second, the mixed liquid after premixing the first material stream output from the pretreatment unit with the ionic liquid enters a heater and is heated to 80 - 150 °C and depressurized to 0 - 0.5 MPaG.

[0027] Third, the mixed liquid output from the heater enters a solvent devolatilizer. The pressure in the solvent devolatilizer is -0.1 - 0.3 MPaG, and the temperature is 80 - 150 °C, so that the solvent in the mixed liquid is discharged from the devolatilization outlet of the solvent devolatilizer in a gaseous phase, and the remaining mixed liquid is recorded as the second material stream and discharged from the fluid outlet of the solvent devolatilizer, and the mass ratio of the polymer to the ionic liquid in the second material stream is 1:1 - 5.

[0028] Fourth, the second material stream discharged from the fluid outlet of the solvent devolatilizer enters a heat exchanger and exchanges heat with the polymer solution in the pretreatment unit. After heat exchange, the temperature of the second material stream is reduced to 40 - 80 °C, and the pressure is 0 - 0.1 MPaG.

[0029] Fifth, the second material stream after heat exchange enters the dispersion mixer through the mixed liquid feed inlet, and the ionic liquid is input into the dispersion mixer from the ionic liquid feed inlet, so that the polymer in the second material stream precipitates, and then is output from the fluid discharge outlet of the dispersion mixer. In the dispersion mixer, the flow rate ratio of the second material stream to the ionic liquid is 1:10 - 30; the flow rate ratio of the second material stream to the ionic liquid is 10:5 - 30.

[0030] Six, the fluid material output from the fluid outlet of the dispersion mixer enters the settling tank for settling separation to obtain the upper clear liquid and the lower turbid liquid. The upper clear liquid is an ionic liquid and is output from the first separation outlet, and the lower turbid liquid is a polymer with a liquid phase and is output through the second separation outlet;

[0031] Seven, the polymer with a liquid phase output from the second separation outlet of the settling tank is transported to a filtration unit for filtration. The filtrate obtained is an ionic liquid and is output through the second filtration outlet. The filter cake obtained is input into a washing unit and washed with an ionic liquid to finally obtain the polymer after devolatilization separation; the fluid with ionic liquid and impurities after washing is output through the impurity fluid outlet.

[0032] Preferably, the filtrate output from the second filtration outlet and the fluid output from the impurity fluid outlet in step seven are both input into an ionic liquid recovery unit, so that the impurities react with the chemical reagent and are discharged from the impurity outlet, thereby obtaining a purified ionic liquid; and the purified ionic liquid enters the ionic liquid intermediate tank. The upper clear liquid in step six is input into the ionic liquid intermediate tank. The ionic liquid in the ionic liquid intermediate tank is divided into three paths. The first path is transported to the washing unit through the input port of the washing unit, the second path is transported to the dispersion mixer through the ionic liquid feed port of the dispersion mixer, and the third path is transported to the second pipeline.

[0033] Preferably, the flow rate ratio of the ionic liquid in the first path to the ionic liquid in the third path is 1:1 to 5.

[0034] In the above solution, preferably, the polymer is at least one of polyimide, polyamide, ethylene propylene diene monomer rubber, polyolefin elastomer, polyacrylonitrile, and polymethyl methacrylate; the solvent in the polymer solution is at least one of benzene, cyclohexene, acetone, cyclohexane, toluene, n-heptane, n-hexane, and 1-octane.

[0035] Preferably, the ionic liquid is at least one of 1-allyl-3-methylimidazolium dicyanamide (abbreviated as [AMIM][DCA]), 1-ethyl-3-methylimidazolium thiocyanate (abbreviated as [EMIM][SCN]), 1-butyl-3-methylimidazolium thiocyanate (abbreviated as [BMIM][SCN]), 1-butyl-3-methylimidazolium tetrafluoroborate (abbreviated as [BMIM][BF4]), 1-methyl-3-methylimidazolium dimethyl phosphate (abbreviated as [MMIM][DMP]), 1-hexyl-3-methylimidazolium tetrafluoroborate (abbreviated as [HMIM][BF4]), and 1-octyl-3-methylimidazolium tetrafluoroborate (abbreviated as [OMIM][BF4]).

[0036] Compared with the prior art, the advantages of the present invention are as follows: The present invention uses ionic liquid addition for devolatilization separation of polymer solution, which can solve the problems of poor fluidity and difficult dispersion of polymers during devolatilization, and the more difficult separation with increasing polymer concentration, enabling polymer separation to be completed at a lower temperature, facilitating the convenient, efficient and continuous production of polymer particles with uniform size distribution of the obtained polymer particles;

[0037] Moreover, the present application uses normal pressure and low temperature operating conditions to replace the traditional high temperature and high vacuum conditions, effectively reducing the temperature of flash devolatilization, replacing the traditional "devolatilization + extrusion" process, simplifying the process and saving equipment costs while;

[0038] The devolatilization effect of the present invention is comparable to that of the conventional devolatilization process. By adding ionic liquid, the devolatilization temperature is reduced. The produced polymer product has less metal ash content, lower contents of additives, residual monomers and solvents in the polymer product, high purity, and can produce optical grade polymers, with high economic efficiency;

[0039] Due to the addition of a pretreatment unit for the polymer solution, the heat after flash devolatilization is reasonably utilized to provide heat to the pretreatment unit, increasing the devolatilization effect while saving energy and reducing the devolatilization load of subsequent units; and the filtration unit and washing unit in the present application are both conventional designs in the polymer industry and are general equipment, with lower equipment costs than using a complete set of devolatilization devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention;

[0041] Figure 2 It is a schematic structural diagram of the comparative example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0043] Embodiment 1:

[0044] As Figure 1 shown, it is a preferred Embodiment 1 of a system and process for devolatilization separation of polymer solution of the present invention. The system includes a pretreatment unit 1, a heater 2, a solvent devolatilizer 3, a dispersion mixer 4, a sedimentation tank 5, a filtration unit, a washing unit, a heat exchanger 7, an ionic liquid recovery unit 8, and an ionic liquid intermediate tank 9.

[0045] Among them, the pretreatment unit 1 is used to heat the polymer solution and has a solution inlet 11 for input of the polymer solution and a solution outlet 12 for output of the polymer solution.

[0046] The heater 2 is a pipeline heater, which is used to heat up and reduce the pressure of the mixture composed of the polymer solution and the ionic liquid, and has a heating inlet 21 for the input of the mixture and a heating outlet 22 for the output of the mixture. The heating inlet 21 is communicated with the solution outlet 12 of the pretreatment unit 1 through a first pipeline 23, and a second pipeline 24 for transporting the ionic liquid is communicated with the first pipeline 23.

[0047] The solvent devolatilizer 3 is used to reduce the pressure of the heated mixture to a slightly positive pressure state to evaporate the solvent, and has a devolatilization inlet 31 communicated with the heating outlet 22 of the above-mentioned heater 2, a devolatilization outlet 32 for discharging the flash vapor, and a fluid outlet 33.

[0048] The dispersion mixer 4 is used to precipitate the polymer in powder form, and has a mixture feed inlet 41 communicated with the fluid outlet 33 of the above-mentioned solvent devolatilizer 3, an ionic liquid feed inlet 42 for the input of the ionic liquid, and a fluid discharge outlet 43. In this embodiment, the dispersion mixer 4 can be prepared by itself or can adopt the equipment disclosed in the invention patent "A System for Precipitating Polymer Solution into Solid Powder and a Continuous Precipitation Method" (the authorized announcement number is CN109749099B) with the patent number of 201910145891.2.

[0049] The sedimentation tank 5 is used for sedimentation separation of the polymer and the ionic liquid, and has a separation inlet 51 communicated with the fluid discharge outlet 43 of the above-mentioned dispersion mixer 4, a first separation outlet 52 for the output of the separated ionic liquid, and a second separation outlet 53 for the output of the separated polymer with liquid phase.

[0050] The filtering unit is used to filter out the residual liquid phase in the separated polymer, and has a filtering inlet communicated with the second separation outlet 53 of the above-mentioned sedimentation tank 5, a first filtering outlet for the output of the filtered polymer, and a second filtering outlet for the output of the filtered liquid phase.

[0051] The washing unit has a washing inlet, a washing outlet, an input port for the input of the ionic liquid, and an impurity fluid outlet for the output of the fluid with ionic liquid and impurities after washing. Its washing inlet is communicated with the first filtering outlet of the above-mentioned filtering unit, and its washing outlet is used for the output of the washed polymer, so as to obtain the polymer after devolatilization and separation.

[0052] The heat exchanger 7 has a cold medium channel 71 and a hot medium channel 72. The fluid outlet 33 of the solvent devolatilizer 3 is communicated with the mixture feed inlet 41 of the dispersion mixer 4 through the above-mentioned hot medium channel 72. The inlet and outlet of the cold medium channel 71 are both communicated with the pretreatment unit 1 through their respective pipelines, and are used to heat the polymer solution in the pretreatment unit 1.

[0053] The ionic liquid recovery unit 8 has a recovery inlet 81 communicating with the above-mentioned second filtration outlet and the impurity fluid outlet, a chemical reagent inlet 82 for the entry of a chemical reagent capable of chemically reacting with the above-mentioned impurities, an inert gas inlet for the entry of inert gas (in this embodiment, the inert gas is input from the chemical reagent inlet 82, that is, the inert gas inlet and the chemical reagent inlet 82 are the same inlet), a recovery outlet 83 for outputting the ionic liquid from which impurities have been removed, and an impurity outlet 84 for outputting the reacted impurities. The recovery outlet 83 communicates with the above-mentioned second pipeline 24, the ionic liquid feed inlet 42 of the dispersion mixer 4, and the input port of the washing unit through an ionic liquid intermediate tank 9. An ionic liquid transfer pump 91 is provided on the connecting pipeline between the ionic liquid intermediate tank 9, the ionic liquid feed inlet 42 of the dispersion mixer 4, and the input port of the washing unit, and a make-up liquid pipeline 92 for supplementing ionic liquid is connected. And the ionic liquid intermediate tank 9 communicates with the first separation outlet 52 of the sedimentation tank 5.

[0054] In this embodiment, the filtration unit and the washing unit are combined into a filtration and washing unit 6 for filtering and washing the polymer. The filtration and washing unit 6 has an inlet 61 communicating with the first separation outlet 52 of the sedimentation tank 5, a liquid outlet 62 communicating with the recovery inlet 81 of the ionic liquid recovery unit 8 (in this embodiment, an alkali liquid pipeline 85 for transporting alkali liquid is connected to the pipeline where the recovery inlet 81 and the liquid outlet 62 communicate, and the alkali liquid is used to remove the catalyst in the polymer solution), a polymer outlet 63 for outputting the washed polymer, and an ionic liquid inlet 64 communicating with the ionic liquid intermediate tank 9. And in this embodiment, a polymer transfer pump 54 is provided on the connecting pipeline between the first separation outlet 52 of the sedimentation tank 5 and the inlet 61 of the filtration and washing unit 6, and the polymer transfer pump 54 is at least one of a diaphragm pump, a plunger pump, and a gear pump.

[0055] The steps of the devolatilization separation process for the polymer solution using the system of this embodiment are as follows:

[0056] I. The polymer solution coming from the reaction unit (the polymer in this embodiment is ethylene / 1-butene copolymer elastomer, and the solvent is n-hexane) enters the pretreatment unit 1 for heating and evaporation to obtain a first stream. The first stream is a polymer homogeneous solution, with a temperature of 80 °C, a pressure of 2.4 MPaG, a flow rate of 60 Kg / Hr, and the concentration of the polymer in the first stream is 45 wt%, the content of C4H8 is 15.6 wt%, the content of C6H 14 is 38.8 wt%, the content of the additive is 0.1 wt%, and the content of the oligomer is 0.5 wt%;

[0057] II. The mixture of the first logistics output from the pretreatment unit 1 and the ionic liquid (in this embodiment, the ionic liquid is 1-octyl-3-methylimidazolium tetrafluoroborate (abbreviated as [OMIM][BF4])) enters the heater 2 and is heated to 100 °C and depressurized to 0.3 MPaG; the content of the first logistics in the mixture can be adjusted by a flow regulating valve, and this flow regulating valve is located on the first pipeline 23.

[0058] III. The mixture output from the heater 2 enters the solvent devolatilizer 3. The pressure inside the solvent devolatilizer 3 is 0.2 MPaG and the temperature is 120 °C, so that the solvent in the mixture is discharged in gaseous form from the devolatilization outlet 32 of the solvent devolatilizer 3, and the remaining mixture is recorded as the second logistics and discharged from the fluid outlet 33 of the solvent devolatilizer 3, and the mass ratio of the polymer to the ionic liquid in the second logistics is 1:1; in this embodiment, the pressure inside the solvent devolatilizer 3 can be controlled by a pressure regulating valve.

[0059] IV. The second logistics discharged from the fluid outlet 33 of the solvent devolatilizer 3 enters the heat exchanger 7 and exchanges heat with the polymer solution in the pretreatment unit 1. After heat exchange, the temperature of the second logistics is reduced to 40 - 80 °C and the pressure is 0.08 MPaG;

[0060] V. The second logistics after heat exchange enters the dispersion mixer 4 through the mixture feed port 41, and the ionic liquid is input into the dispersion mixer 4 from the ionic liquid feed port 42, so that the polymer in the second logistics precipitates, and then is output from the fluid discharge port 43 of the dispersion mixer 4. Inside the dispersion mixer 4, the flow velocity ratio of the second logistics to the ionic liquid is 1:15; the flow rate ratio of the second logistics to the ionic liquid is 10:7;

[0061] VI. The fluid material output from the fluid discharge port 43 of the dispersion mixer 4 enters the settling tank 5 for settling separation to obtain the upper clear liquid and the lower turbid liquid. The upper clear liquid is the ionic liquid and is output from the first separation outlet 52, and the lower turbid liquid is the polymer with a liquid phase and is output through the second separation outlet 53; the polymer with a liquid phase output from the second separation outlet 53 of the settling tank 5 is recorded as the sixth logistics. The temperature of the sixth logistics is 40 °C, the pressure is 0.05 MPaG, the flow rate is 16.2 Kg / Hr, and the content of the polymer is 82.3 wt%, the content of the ionic liquid is 6.84 wt%, the content of the auxiliary agent is 0.01 wt%, and the content of the oligomer is 0.05 wt%.

[0062] VII. The polymer with liquid phase output from the second separation outlet 53 of the settling tank 5 is transported to a filtration unit for filtration. The filtrate obtained is an ionic liquid and is output through the second filtration outlet. The filter cake obtained is input into a washing unit and washed with the ionic liquid. Finally, the polymer after devolatilization separation is obtained, and the polymer after devolatilization separation is denoted as the seventh stream. The concentration of n-hexane in the seventh stream is 48 ppm; the fluid with ionic liquid and impurities after washing is output through the impurity fluid outlet.

[0063] In step VII, the filtrate output from the second filtration outlet and the fluid output from the impurity fluid outlet are both input into the ionic liquid recovery unit 8, so that the impurities react with the chemical reagent and are discharged from the impurity outlet 84, thereby obtaining the purified ionic liquid; and the purified ionic liquid enters the ionic liquid intermediate tank 9. The supernatant in step VI is input into the ionic liquid intermediate tank 9. The ionic liquid in the ionic liquid intermediate tank 9 is divided into three paths. The first path is transported to the washing unit through the input port of the washing unit. The second path is transported to the dispersion mixer 4 through the ionic liquid feed port 42 of the dispersion mixer 4. The third path is transported to the second pipeline 24. And the flow rate ratio of the ionic liquid in the first path to the ionic liquid in the third path is 4:3.

[0064] Example 2:

[0065] This example is basically the same as Example 1, except that the pressure in the solvent devolatilizer 3 in this example is -0.05 MPaG, and the mass concentration of the polymer in the sixth stream output from the second separation outlet 53 of the settling tank 5 is 87.7 wt%. The concentration of n-hexane in the seventh stream output from the filtration and washing unit 6 is 36 ppm.

[0066] Example 3:

[0067] This example is basically the same as Example 1, except that the concentration of the polymer in the first stream in this example is 25 wt%, and the mass concentration of the polymer in the sixth stream output from the second separation outlet 53 of the settling tank 5 is 80.5 wt%. The concentration of n-hexane in the seventh stream output from the filtration and washing unit 6 is 65 ppm.

[0068] Example 4:

[0069] This example is basically the same as Example 1, except that the temperature of the heater 2 in this example is 80 °C, the temperature in the solvent devolatilizer 3 is 100 °C, and the mass concentration of the polymer in the sixth stream output from the second separation outlet 53 of the settling tank 5 is 78.3 wt%. The concentration of n-hexane in the seventh stream output from the filtration and washing unit 6 is 70 ppm.

[0070] Example 5:

[0071] This embodiment is basically the same as Embodiment 1, except that the devolatilization separation processes of the two are slightly different. The process steps of this embodiment are as follows:

[0072] 1. The polymer solution coming from the reaction unit (the polymer in this embodiment is ethylene / 1-butene copolymer elastomer, and the solvent is n-hexane) enters the pretreatment unit 1 for heating and evaporation to obtain the first stream. The first stream is a polymer homogeneous solution with a temperature of 80°C, a pressure of 2.4 MPaG, a flow rate of 60 Kg / Hr, and the concentration of the polymer in the first stream is 10 wt%.

[0073] 2. The mixture obtained by mixing the first stream output from the pretreatment unit 1 with the ionic liquid (the ionic liquid in this embodiment is 1-butyl-3-methylimidazole thiocyanate (abbreviated as [BMIM][SCN])) enters the heater 2 and is heated to 150°C and depressurized to 0.5 MPaG. The content of the first stream in the mixture can be adjusted by a flow control valve, and this flow control valve is located on the first pipeline 23.

[0074] 3. The mixture output from the heater 2 enters the solvent devolatilizer 3. The pressure inside the solvent devolatilizer 3 is 0.3 MPaG and the temperature is 80°C, so that the solvent in the mixture is discharged from the devolatilization outlet 32 of the solvent devolatilizer 3 in the form of gas phase, and the remaining mixture is recorded as the second stream and discharged from the fluid outlet 33 of the solvent devolatilizer 3. The mass ratio of the polymer to the ionic liquid in the second stream is 1:5. In this embodiment, the pressure inside the solvent devolatilizer 3 can be controlled by a pressure control valve.

[0075] 4. The second stream discharged from the fluid outlet 33 of the solvent devolatilizer 3 enters the heat exchanger 7 and exchanges heat with the polymer solution in the pretreatment unit 1. After heat exchange, the temperature of the second stream is reduced to 60°C and the pressure is 0.1 MPaG.

[0076] 5. The second stream after heat exchange enters the dispersion mixer 4 through the mixed liquid feed port 41, and the ionic liquid is input into the dispersion mixer 4 from the ionic liquid feed port 42, so that the polymer in the second stream precipitates, and then is output from the fluid discharge port 43 of the dispersion mixer 4. In the dispersion mixer 4, the flow rate ratio of the second stream to the ionic liquid is 1:30; the flow rate ratio of the second stream to the ionic liquid is 10:30.

[0077] 6. The fluid material output from the fluid discharge port 43 of the dispersion mixer 4 enters the sedimentation tank 5 for sedimentation separation to obtain the upper clear liquid and the lower turbid liquid. The upper clear liquid is the ionic liquid and is output from the first separation outlet 52, and the lower turbid liquid is the polymer with liquid phase and is output through the second separation outlet 53. The polymer with liquid phase output from the second separation outlet 53 of the sedimentation tank 5 is recorded as the sixth stream.

[0078] VII. The polymer with liquid phase output from the second separation outlet 53 of the settling tank 5 is transported to the filtration unit for filtration. The filtrate obtained is ionic liquid and is output through the second filtration outlet. The filter cake obtained is input into the washing unit and washed with ionic liquid, and finally the polymer after devolatilization separation is obtained. The polymer after devolatilization separation is denoted as the seventh stream; the fluid with ionic liquid and impurities after washing is output through the impurity fluid outlet.

[0079] In step VII, the filtrate output from the second filtration outlet and the fluid output from the impurity fluid outlet are both input into the ionic liquid recovery unit 8, so that the impurities react with the chemical reagent and are discharged from the impurity outlet 84, thereby obtaining purified ionic liquid; and the purified ionic liquid enters the ionic liquid intermediate tank 9. The supernatant in step VI is input into the ionic liquid intermediate tank 9. The ionic liquid in the ionic liquid intermediate tank 9 is divided into three paths. The first path is transported to the washing unit through the inlet of the washing unit. The second path is transported to the dispersing mixer 4 through the ionic liquid feed port 42 of the dispersing mixer 4. The third path is transported to the second pipeline 24. And the flow rate ratio of the ionic liquid in the first path to the ionic liquid in the third path is 1:1.

[0080] Example 6:

[0081] This example is basically the same as Example 1, except that the devolatilization separation processes of the two are slightly different. The process steps of this example are as follows:

[0082] I. The polymer solution coming from the reaction unit (the polymer in this example is ethylene / 1-butene copolymer elastomer and the solvent is n-hexane) enters the pretreatment unit 1 for heating and evaporation to obtain the first stream. The first stream is a polymer homogeneous solution with a temperature of 80 °C, a pressure of 2.4 MPaG, a flow rate of 60 Kg / Hr, and the concentration of the polymer in the first stream is 50 wt%.

[0083] II. The mixture of the first stream output from the pretreatment unit 1 and the ionic liquid (the ionic liquid in this example is 1-hexyl-3-methylimidazolium tetrafluoroborate (abbreviated as [HMIM][BF4])) enters the heater 2 and is heated to 110 °C and depressurized to 0 MPaG; the content of the first stream in the mixture can be adjusted by a flow regulating valve, and this flow regulating valve is located on the first pipeline 23.

[0084] III. The mixed liquid output from the heater 2 enters the solvent devolatilizer 3. The pressure inside the solvent devolatilizer 3 is -0.1 MPaG and the temperature is 150 °C, such that the solvent in the mixed liquid is discharged in gaseous form from the devolatilization outlet 32 of the solvent devolatilizer 3. The remaining mixed liquid is denoted as the second stream and is discharged from the fluid outlet 33 of the solvent devolatilizer 3. Moreover, the mass ratio of the polymer to the ionic liquid in the second stream is 1:3. In this embodiment, the pressure inside the solvent devolatilizer 3 can be controlled by a pressure regulating valve.

[0085] IV. The second stream discharged from the fluid outlet 33 of the solvent devolatilizer 3 enters the heat exchanger 7 and exchanges heat with the polymer solution in the pretreatment unit 1. After heat exchange, the temperature of the second stream drops to 40 °C and the pressure is 0 MPaG.

[0086] V. The second stream after heat exchange enters the dispersion mixer 4 through the mixed liquid feed port 41, and the ionic liquid is input into the dispersion mixer 4 from the ionic liquid feed port 42, causing the polymer in the second stream to precipitate, and then it is output from the fluid discharge port 43 of the dispersion mixer 4. Inside the dispersion mixer 4, the flow rate ratio of the second stream to the ionic liquid is 1:10; the flow rate ratio of the second stream to the ionic liquid is 10:5.

[0087] VI. The fluid material output from the fluid discharge port 43 of the dispersion mixer 4 enters the settling tank 5 for settling separation to obtain the upper clear liquid and the lower turbid liquid. Among them, the upper clear liquid is the ionic liquid and is discharged from the first separation outlet 52, and the lower turbid liquid is the polymer with a liquid phase and is discharged through the second separation outlet 53. The polymer with a liquid phase discharged from the second separation outlet 53 of the settling tank 5 is denoted as the sixth stream.

[0088] VII. The polymer with a liquid phase discharged from the second separation outlet 53 of the settling tank 5 is transported to the filtration unit for filtration. The filtrate obtained is the ionic liquid and is discharged through the second filtration outlet. The filter cake is input into the washing unit and washed with the ionic liquid to finally obtain the polymer after devolatilization separation. Moreover, the polymer after devolatilization separation is denoted as the seventh stream; the fluid with the ionic liquid and impurities after washing is discharged through the impurity fluid outlet.

[0089] In Step 7, the filtrate output from the second filtration outlet and the fluid output from the impurity fluid outlet are both input into the ionic liquid recovery unit 8, enabling the impurities to react with the chemical reagent and be discharged from the impurity outlet 84, thereby obtaining purified ionic liquid; and the purified ionic liquid enters the ionic liquid intermediate tank 9, and the supernatant in Step 6 is input into the ionic liquid intermediate tank 9. The ionic liquid in the ionic liquid intermediate tank 9 is divided into three paths. The first path is transported to the washing unit through the input port of the washing unit, the second path is transported to the dispersion mixer 4 through the ionic liquid feed port 42 of the dispersion mixer 4, and the third path is transported to the second pipeline 24. And the flow rate ratio of the ionic liquid in the first path to the ionic liquid in the third path is 3:1.

[0090] Comparative Example 1:

[0091] As Figure 2 shown, the system and process for devolatilization separation of polymer solution in this comparative example include three solvent devolatilizers 3', namely a primary solvent devolatilizer 3a', a secondary solvent devolatilizer 3b', and a tertiary solvent devolatilizer 3c'. Upstream of each solvent devolatilizer 3' is connected with a heater 2', namely a primary heater 2a' connected to the primary solvent devolatilizer 3a', a secondary heater 2b' connected to the secondary solvent devolatilizer 3b', and a tertiary heater 2c' connected to the tertiary solvent devolatilizer 3c'. Meanwhile, the downstream of the tertiary solvent devolatilizer 3c' is connected with a polymer extrusion granulation unit 10'.

[0092] The process of this comparative example is as follows:

[0093] I. The polymer solution coming from the reaction unit (the polymer in this example is ethylene / 1-butene copolymer elastomer, and the solvent is n-hexane) is denoted as the first stream. The first stream is a polymer homogeneous solution with a temperature of 80°C, a pressure of 2.4 MPaG, a flow rate of 60 Kg / Hr, and the concentration of the polymer in the first stream is 45 wt%, the content of C4H8 is 15.6 wt%, the content of C6H14 is 38.8 wt%, the content of the additive is 0.1 wt%, and the content of the oligomer is 0.5 wt%.

[0094] II. The first stream enters the primary heater 2a' and is heated to 180°C, and then enters the primary solvent devolatilizer 3a', and its pressure flashes from 2.4 MPaG to 1.5 MPaG.

[0095] III. The fluid coming out of the primary solvent devolatilizer 3a' enters the secondary heater 2b' and is heated to 200°C, and then enters the secondary solvent devolatilizer 3b', and its pressure flashes from 1.5 MPaG to 1 MPaG.

[0096] IV. The fluid coming out of the secondary solvent devolatilizer 3b' enters the tertiary heater 2c' and is heated to 220 °C, and then enters the tertiary solvent devolatilizer 3c', where its pressure flashes from 1 MPaG to 0.3 MPaG; the fluid coming out of the tertiary solvent devolatilizer 3c' is denoted as the sixth stream. The temperature of the sixth stream is 220 °C, the pressure is 0.2 MPaG, the flow rate is 16.7 Kg / Hr, and the polymer content is 80.7 wt%, the C4H8 content is 1.2 wt%, the C6H 14 content is 8.2 wt%, the additive content is 0.1 wt%, and the oligomer content is 0.5 wt%.

[0097] V. The sixth stream enters the polymer extrusion granulation unit 10' for devolatilization extrusion and granulation. The stream coming out of the polymer extrusion granulation unit 10' is denoted as the seventh stream, and the concentration of n-hexane in the seventh stream is 85 ppm.

[0098] Comparative Example 2:

[0099] It is basically the same as Comparative Example 1, except that in this comparative example, the pressure of the tertiary solvent devolatilizer is -0.05 MPaG, the polymer content in the sixth stream is 84.3 wt%, and the concentration of n-hexane in the seventh stream is 50 ppm.

[0100] By comparing the results of the examples of this application and the comparative examples, it can be seen that this application uses ionic liquid addition for devolatilization separation of polymer solutions, replacing the traditional "devolatilization + extrusion" process, using normal pressure and low temperature operating conditions instead of traditional high temperature and vacuum conditions; and adding a polymer solution pretreatment unit, reasonably utilizing the heat after flash devolatilization to provide heat for the pretreatment unit, increasing the devolatilization effect while saving energy and reducing the devolatilization load of subsequent units; at the same time, the polymer filtration and washing units added in this application are conventional designs in the polymer industry and are all general equipment, and the equipment cost is lower than that of using a complete set of devolatilization devices; and the post-treatment of this application cancels the patented equipment devolatilization device and vacuum extruder, greatly saving equipment investment and operation difficulty. The devolatilization effect of this application is comparable to that of the conventional devolatilization process. By adding ionic liquid, the devolatilization temperature is reduced, the produced polymer product has less metal ash, the contents of additives, residual monomers and solvents in the polymer product are lower, the purity is high, optical grade polymers can be produced, and it has high economy.

Claims

1. A system for devolatilization separation of polymer solutions, characterized in that It includes: A pretreatment unit (1) for heating a polymer solution, having a solution inlet (11) for inputting the polymer solution and a solution outlet (12) for outputting the polymer solution; A heater (2) for heating up and reducing the pressure of a mixture of the polymer solution and an ionic liquid, having a heating inlet (21) for inputting the mixture and a heating outlet (22) for outputting the mixture. The heating inlet (21) is connected to the solution outlet (12) of the above-mentioned pretreatment unit (1) through a first pipeline (23), and a second pipeline (24) for transporting the ionic liquid is connected to the first pipeline (23); A solvent devolatilizer (3) for reducing the pressure of the heated mixture to a slightly positive pressure state to evaporate the solvent, having a devolatilization inlet (31) connected to the heating outlet (22) of the above-mentioned heater (2), a devolatilization outlet (32) for discharging the flash vapor, and a fluid outlet (33); A dispersion mixer (4) for precipitating the polymer in powder form, having a mixture feed port (41) connected to the fluid outlet (33) of the above-mentioned solvent devolatilizer (3), an ionic liquid feed port (42) for inputting the ionic liquid, and a fluid discharge port (43); A settling tank (5) for settling and separating the polymer and the ionic liquid, having a separation inlet (51) connected to the fluid discharge port (43) of the above-mentioned dispersion mixer (4), a first separation outlet (52) for outputting the separated ionic liquid, and a second separation outlet (53) for outputting the separated polymer with a liquid phase; A filtration unit for filtering out the residual liquid phase in the separated polymer, having a filtration inlet connected to the second separation outlet (53) of the above-mentioned settling tank (5) and a first filtration outlet for outputting the filtered polymer; A washing unit having a washing inlet and a washing outlet. The washing inlet is connected to the first filtration outlet of the above-mentioned filtration unit, and the washing outlet is used for outputting the washed polymer, thereby obtaining the polymer after devolatilization and separation.

2. The system according to claim 1, wherein: It further includes a heat exchanger (7) having a cold medium channel (71) and a hot medium channel (72). The fluid outlet (33) of the solvent devolatilizer (3) is connected to the mixture feed port (41) of the dispersion mixer (4) through the above-mentioned hot medium channel (72). The inlets and outlets of the cold medium channel (71) are both connected to the above-mentioned pretreatment unit (1) through their respective pipelines for heating the polymer solution in the pretreatment unit (1).

3. The system according to claim 2, characterized in that: The washing unit further has an input port for inputting the ionic liquid.

4. The system according to claim 3, characterized in that: The filtration unit further has a second filtration outlet for outputting the filtered liquid phase; The washing unit further has an impurity fluid outlet for outputting the washed fluid having the ionic liquid and impurities; The system further includes an ionic liquid recovery unit (8), which has a recovery inlet (81) communicating with the second filtration outlet and the impurity fluid outlet described above, a chemical reagent inlet (82) for a chemical reagent capable of chemically reacting with the above-mentioned impurities to enter, an inert gas inlet for inert gas to enter, a recovery outlet (83) for outputting the ionic liquid from which impurities have been removed, and an impurity outlet (84) for outputting the reacted impurities. The recovery outlet (83) communicates with the second pipeline (24), the ionic liquid feed port (42) of the dispersion mixer (4), and the input port of the washing unit.

5. The system according to claim 4, characterized in that: The system further includes an ionic liquid intermediate tank (9). The recovery outlet (83) of the ionic liquid recovery unit (8) communicates with the second pipeline (24), the ionic liquid feed port (42) of the dispersion mixer (4), and the input port of the washing unit through the ionic liquid intermediate tank (9); and the ionic liquid intermediate tank (9) communicates with the first separation outlet (52) of the sedimentation tank (5).

6. A process for devolatilizing and separating a polymer solution using the system as described in claim 5, characterized in that The steps are as follows: I. The polymer solution coming from the reaction unit enters the pretreatment unit (1) for heating and evaporation to obtain a first material flow, and the first material flow is a polymer homogeneous solution with a concentration of 10-50 wt%. II. The mixed liquid after premixing the first material flow output from the pretreatment unit (1) with the ionic liquid enters the heater (2), is heated to 80-150 °C, and the pressure is reduced to 0-0.5 MPaG. III. The mixed liquid output from the heater (2) enters the solvent devolatilizer (3). The pressure in the solvent devolatilizer (3) is -0.1-0.3 MPaG, and the temperature is 80-150 °C, so that the solvent in the mixed liquid is discharged from the devolatilization outlet (32) of the solvent devolatilizer (3) in a gaseous form. The remaining mixed liquid is denoted as the second material flow and is discharged from the fluid outlet (33) of the solvent devolatilizer (3), and the mass ratio of the polymer to the ionic liquid in the second material flow is 1:1-5. IV. The second material flow discharged from the fluid outlet (33) of the solvent devolatilizer (3) enters the heat exchanger (7) and exchanges heat with the polymer solution in the pretreatment unit (1). After heat exchange, the temperature of the second material flow is reduced to 40-80 °C, and the pressure is 0-0.1 MPaG. V. The second material flow after heat exchange enters the dispersion mixer (4) through the mixed liquid feed port (41), and the ionic liquid is input into the dispersion mixer (4) from the ionic liquid feed port (42), so that the polymer in the second material flow precipitates, and then is output from the fluid discharge port (43) of the dispersion mixer (4). In the dispersion mixer (4), the flow rate ratio of the second material flow to the ionic liquid is 1:10-30; the flow rate ratio of the second material flow to the ionic liquid is 10:5-30. VI. The fluid material output from the fluid discharge port (43) of the dispersion mixer (4) enters the sedimentation tank (5) for sedimentation separation to obtain an upper clear liquid and a lower turbid liquid. The upper clear liquid is the ionic liquid and is output from the first separation outlet (52), and the lower turbid liquid is the polymer with a liquid phase and is output through the second separation outlet (53). VII. The polymer with liquid phase output from the second separation outlet (53) of the settling tank (5) is transported to a filtration unit for filtration. The filtrate obtained is ionic liquid and is output through the second filtration outlet. The filter cake obtained is input into a washing unit and washed with ionic liquid to finally obtain the polymer after devolatilization and separation; The fluid with ionic liquid and impurities after washing is output through the impurity fluid outlet.

7. The process according to claim 6, characterized in that: The filtrate output from the second filtration outlet and the fluid output from the impurity fluid outlet in step VII are both input into the ionic liquid recovery unit (8), so that the impurities react with the chemical reagent and are discharged from the impurity outlet (84), thereby obtaining purified ionic liquid; and the purified ionic liquid enters the ionic liquid intermediate tank (9). The supernatant in step VI is input into the ionic liquid intermediate tank (9). The ionic liquid in the ionic liquid intermediate tank (9) is divided into three paths. The first path is transported to the washing unit through the input port of the washing unit. The second path is transported to the dispersion mixer (4) through the ionic liquid feed port (42) of the dispersion mixer (4). The third path is transported to the second pipeline (24).

8. The process according to claim 7, characterized in that: The flow rate ratio of the ionic liquid in the first path to the ionic liquid in the third path is 1-3:

1.

9. The process according to claim 6, characterized in that: The polymer is at least one of polyimide, polyamide, ethylene propylene diene monomer, polyolefin elastomer, polyacrylonitrile, and polymethyl methacrylate; the solvent in the polymer solution is at least one of benzene, cyclohexene, acetone, cyclohexane, toluene, n-heptane, n-hexane, and 1-octane.

10. The process according to claim 6, characterized in that: The ionic liquid is at least one of 1-allyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-methyl-3-methylimidazolium dimethylphosphate, 1-hexyl-3-methylimidazolium tetrafluoroborate, and 1-octyl-3-methylimidazolium tetrafluoroborate.

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