A method for preparing polycarbonate by low-temperature positive pressure synthesis

Abstract

The present invention provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, the method comprising the following steps: (1) mixing the ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and dihydroxy compound with non-alcoholic polar organic matter, carrying out polycondensation reaction, and obtaining light phase material and heavy phase material through liquid-liquid separation process; (2) flashing and extruding the heavy phase material in step (1) to obtain the polycarbonate. The present invention adds non-alcoholic polar organic matter to extract phenol generated by the polycondensation reaction in the polycondensation reaction of polycarbonate preparation, so that the polycondensation reaction is carried out under low temperature and positive pressure conditions, and the obtained polycarbonate has the characteristics of high number average molecular weight, low yellowness index and high quality.

Description

Technical Field

[0001] The invention belongs to the technical field of polycarbonate, and in particular relates to a preparation method of low-temperature positive pressure synthesized polycarbonate. Background Art

[0002] Polycarbonate (PC) is a transparent resin with high strength, high toughness, high heat resistance, high shock resistance and good processing performance. At present, there are two main methods for the production of polycarbonate: one is the phosgene method; the other is the melt method. In the early days, most manufacturers used the phosgene method. However, because phosgene is highly toxic and the public is paying more and more attention to environmental issues, newly built PC production bases basically use the more environmentally friendly melt method. However, the polycarbonate produced by the melt method is still inferior to the phosgene method in some properties, mainly because the operating temperature of the phosgene method is much lower than that of the melt method. Studies have shown that the higher the temperature, the greater the impact on polycarbonate. As the reaction temperature increases, the branching and cross-linking products increase, and the degradation increases (Deng Cheng. Synthesis of polycarbonate by melt ester exchange and process exploration. Qingdao University of Science and Technology, 2017.).

[0003] For the preparation of PC by the melt process, the polycondensation reaction is a reversible reaction. Only by continuously removing small molecules can the reaction degree of polycarbonate be increased (molecular weight be increased). However, as the reactants in the system decrease and the molecular weight of polycarbonate increases, the viscosity of the system increases sharply. Usually, the viscosity of the last polycondensation reactor can reach about 300 to 1000 Pa·S at the operating temperature of the polycondensation reactor. In this case, in order to increase the molecular weight of the polymer (increase the forward reaction rate), the only way is to increase the temperature and vacuum degree.

[0004] CN113801313A discloses a method for preparing a high molecular weight polycarbonate and the polycarbonate. The method uses a carbonic acid diester and a dihydroxy compound as raw materials, adds a catalyst and then mixes and preheats, and sequentially carries out ester exchange, pre-polycondensation and final polycondensation reactions under the conditions of a temperature of 210-320°C and an absolute pressure of 0.01-30kPa. The polycarbonate prepared by the preparation method provided by the technical scheme has a narrow molecular weight distribution, and the average molecular weight can reach 4w, but the temperature of the last kettle can be as high as 320°C.

[0005] CN105315445A discloses a polycarbonate synthesis process, which includes uniformly mixing bisphenol A and isosorbide with dimethyl oxalate in a molten state for esterification, and polymerizing the reaction product after the esterification of the two to obtain a bisphenol A-isosorbide copolymer polycarbonate. The temperature of the polycondensation reaction in the polycarbonate synthesis process provided by the technical solution is 250-310°C.

[0006] CN101896535A discloses a method for producing polycarbonate, which includes using at least two reactors in series to melt-polycondense a dihydroxy compound containing a dihydroxy compound having at least one connecting group -CH2-O- in the molecule with a carbonic acid diester to produce polycarbonate, and setting the temperature difference between the polymer temperature in the reactor and the temperature of the heating medium to be below 80°C when the reduced viscosity of the generated polycarbonate is below 0.10dl / g, below 60°C when the reduced viscosity exceeds 0.10dl / g and is less than or equal to 0.40dl / g, and below 40°C when the reduced viscosity exceeds 0.40dl / g. The reaction temperature of the last kettle in the polycondensation process in the production of polycarbonate provided by the technical solution is 210-270°C.

[0007] In the prior art, polycarbonate products with a certain degree of polymerization are prepared by increasing the temperature. However, high temperature also brings side effects. Since the reactants need a certain residence time in the polycondensation reactor, coupled with the high temperature environment, the substances decompose and impurities are generated, causing the polycarbonate to turn yellow, etc., thereby reducing the quality of the polycarbonate.

[0008] Therefore, it is necessary to develop a method for preparing polycarbonate which is environmentally friendly and has high quality. Summary of the invention

[0009] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing polycarbonate by low-temperature positive pressure synthesis. The polycarbonate prepared by the preparation method has the characteristics of high number average molecular weight, low yellowness index and high quality.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] The present invention provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, the preparation method comprising the following steps:

[0012] (1) mixing the ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and a dihydroxy compound with a non-alcoholic polar organic matter, carrying out a polycondensation reaction, and obtaining a light phase substance and a heavy phase substance through a liquid-liquid separation process;

[0013] (2) The heavy phase material of step (1) is flash evaporated and extruded to obtain the polycarbonate.

[0014] In the present invention, the low temperature means a temperature ≤ 220°C, such as 180°C, 182°C, 184°C, 186°C, 190°C, 195°C, 200°C, 205°C, 210°C or 215°C, and the positive pressure means a pressure ≥ 0MPaG, such as 0.1MPaG, 0.5MPaG, 1MPaG, 3MPaG or 5MPaG, etc.

[0015] In the present invention, the light phase material refers to a material with a density of ≤1200 kg / m 3 Materials, such as 700kg / m 3 , 750kg / m 3 , 800kg / m 3 、850kg / m 3 , 900kg / m 3 , 950kg / m 3 , 1000kg / m 3 、1050kg / m 3 , 1100kg / m 3 or 1150kg / m 3 etc., more preferably ≤1100kg / m 3 , and further preferably ≤900kg / m 3 The heavy phase material refers to a material with a density of >1200 kg / m 3 Materials, such as 1250kg / m 3 , 1300kg / m 3 、1350kg / m 3 , 1400kg / m 3 、1450kg / m 3 , 1500kg / m 3 、1550kg / m 3 or 1600kg / m 3 wait.

[0016] In the present invention, the ester exchange material obtained by the ester exchange reaction between diphenyl carbonate and a dihydroxy compound is mixed with a non-alcoholic polar organic matter to carry out a polycondensation reaction, and the by-product of the polycondensation reaction, the small molecular substance phenol, exists in the reaction material of the polycondensation reaction in the form of a liquid. In the reaction material of the polycondensation reaction, the polycarbonate is in a molten state, and the non-alcoholic polar organic matter is in a liquid state. Therefore, in the polycondensation reaction, the polycarbonate melt and the non-alcoholic polar organic matter are basically in a liquid-liquid two-phase state, and the non-alcoholic polar organic matter and phenol are miscible, and the non-alcoholic polar organic matter can dissolve phenol, and is basically insoluble or slightly soluble. In the process of decomposing polycarbonate, phenol is extracted into the liquid phase of non-alcoholic polar organic matter, so that phenol on the surface of the polycarbonate melt is continuously extracted and dissolved, and the phenol inside is continuously diffused out, which can fully extract the phenol generated by the polycondensation reaction, so that the polycondensation reaction proceeds in the positive direction, and there is no need to increase the temperature and vacuum degree to make the reaction proceed in the positive direction, so that the polycondensation reaction can be carried out at a low temperature. Therefore, the polycarbonate melt in the polycondensation reactor stays too long during the polycondensation reaction and will not cause other side reactions, thereby being able to produce polycarbonate with a higher molecular weight, and the obtained polycarbonate has a low yellowness index and high quality.

[0017] Preferably, the dihydroxy compound includes any one or a combination of at least two of bisphenol A, isomannide, isoidide, isosorbide, 1,4-cyclohexanedimethanol or a fluorene-containing dihydroxy compound.

[0018] Preferably, the molar ratio of diphenyl carbonate to the dihydroxy compound is 1:1-1.1, for example, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08 or 1:1.09, etc.

[0019] It should be noted that the catalyst for the transesterification reaction and the catalyst for the polycondensation reaction are not particularly limited in the present invention, and those skilled in the art can select them according to the specific raw materials of diphenyl carbonate and dihydroxy compound.

[0020] Preferably, the catalyst for the transesterification reaction comprises a basic compound.

[0021] Preferably, the basic compound includes any one or a combination of at least two of an alkali metal compound, an alkaline earth metal compound, a basic boron compound, a basic phosphorus compound or a basic ammonium compound.

[0022] Preferably, the catalyst for the polycondensation reaction comprises an acetylacetonate metal complex, and the catalyst for the polycondensation reaction can be selectively added for different polycondensation reaction raw materials.

[0023] It should be noted that the number, temperature, pressure and time of the esterification reactors for the ester exchange reaction of diphenyl carbonate and dihydroxy compounds are not particularly limited in the present invention. Those skilled in the art can select them according to the specific raw materials of diphenyl carbonate and dihydroxy compounds. For example, the ester exchange reaction of diphenyl carbonate and bisphenol A includes sequentially passing through three esterification reactors for ester exchange reaction, and the temperatures of the three esterification reactors passed through in sequence are 190° C., 200° C. and 220° C., respectively, the pressures are 40 KPaA, 10 KPaA and 3 KPaA, respectively, and the residence times are 90 min, 70 min and 80 min, respectively; the ester exchange reaction of diphenyl carbonate, bisphenol A and isosorbide ester includes sequentially passing through three esterification reactors for ester exchange reaction, and the temperatures of the three esterification reactors passed through in sequence are 180° C., 185° C. and 190° C., respectively, the pressures are 35 KPaA, 10 KPaA and 3 KPaA, respectively, and the residence times are 70 min, 70 min and 80 min, respectively.

[0024] Preferably, the non-alcoholic polar organic matter includes any one of dimethylformamide, diethylene glycol butyl ether, ethylene glycol butyl ether, propiophenone or glutaraldehyde, or a combination of at least two thereof.

[0025] Preferably, the mixing in step (1) further comprises adding polyethylene glycol.

[0026] In the present invention, the polyethylene glycol has a very strong solubility for phenolic compounds. Adding polyethylene glycol can improve the extraction effect of phenol and promote the forward reaction.

[0027] Preferably, the number average molecular weight of the polyethylene glycol is ≤400, for example, 200, 220, 240, 260, 280, 300, 320, 340, 360 or 380, etc.

[0028] Preferably, based on the total mass of non-alcoholic polar organic matter and polyethylene glycol as 100%, the mass percentage of the polyethylene glycol is 0-10%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%.

[0029] In the present invention, the total mass of the non-alcoholic polar organic matter and polyethylene glycol is 100%, and the mass percentage of the polyethylene glycol is 0-10%. If the mass percentage of the polyethylene glycol is too large, it will cause difficulty in the subsequent separation of the polyethylene glycol and the polycarbonate, and the energy consumption will increase sharply. In addition, the polyethylene glycol can also dissolve a small amount of polycarbonate, so that too much polycarbonate enters the light phase material, causing loss.

[0030] Preferably, the equipment for the polycondensation reaction in step (1) comprises at least one polycondensation reactor, and the polycondensation reactor is connected to a reactor discharge pump.

[0031] Preferably, the equipment of the liquid-liquid separation process comprises at least one liquid-liquid cyclone, and the liquid-liquid cyclone is connected to the reactor discharge pump.

[0032] Preferably, the light phase substance flowing out of the liquid-liquid cyclone and the gas component obtained by flash evaporation are separated by distillation to obtain phenol and non-alcohol polar organic matter.

[0033] In the present invention, the non-alcohol polar organic matter obtained by distillation separation can be recycled and added to the polycondensation reactor again. When the selected non-alcohol polar organic matter is slightly soluble in polycarbonate, the dissolved polycarbonate will return to the polycondensation reactor together with the recycled non-alcohol polar organic matter to continue to participate in the reaction, thereby reducing the loss of polycarbonate.

[0034] Preferably, the flash distillation equipment comprises a first flash distillation pipeline, a second flash distillation pipeline and a flash distillation devolatilization tank.

[0035] Preferably, the first flash pipe is heated by medium-pressure steam, and the second flash pipe is heated by heat transfer oil.

[0036] Preferably, the heating temperature of the first flash pipe is less than or equal to the heating temperature of the second flash pipe.

[0037] In the present invention, since the liquid phase is the majority in the material in the first flash evaporation pipeline, medium-pressure steam can be used for heating. The medium-pressure steam refers to steam of 2.5MPaG to 5MPaG (e.g., 2.8MPaG, 3MPaG, 3.5MPaG, 4MPaG, 4.5MPaG or 4.8MPaG, etc.). The reasons for selecting medium-pressure steam are: (1) medium-pressure steam is easily available; (2) the steam heat transfer coefficient is larger (compared to heat transfer oil); (3) the steam temperature is constant and it is not easy to make the local temperature too high. As the liquid in the first flash evaporation pipeline is continuously vaporized, there is a lot of gas when it reaches the outlet, the heat transfer is deteriorated, and the heat transfer coefficient in the pipeline is deteriorated. Therefore, only by increasing the heat transfer temperature difference can effective heat transfer be achieved, so the second flash evaporation pipeline should be heated by high-temperature heat transfer oil.

[0038] Preferably, the distillation separation equipment includes a first distillation tower and a second distillation tower.

[0039] Preferably, the distillation separation equipment further comprises a third distillation tower.

[0040] In the present invention, if the boiling point of the non-alcohol polar organic matter is lower than that of phenol, a third distillation tower can be added to the distillation separation equipment. The second distillation tower first returns the non-alcohol polar organic matter separated from the top of the tower to the polycondensation reactor for circulation. Phenol is discharged from the top of the third distillation tower, and the non-alcohol polar organic matter separated from the bottom of the tower is returned to the polycondensation reactor for circulation.

[0041] Preferably, the operating temperature of the polycondensation reactor and the first flash line is independently ≤200°C, for example, 182°C, 184°C, 186°C, 188°C, 190°C, 192°C, 194°C, 196°C or 198°C, etc.

[0042] Preferably, the pressure of the polycondensation reactor is ≥ the larger value of the saturated vapor pressure of the non-alcoholic polar organic matter and the normal pressure at the operating temperature of the polycondensation reactor.

[0043] In the present invention, the pressure of the polycondensation reactor is ≥ the larger value of the saturated vapor pressure of the non-alcoholic polar organic matter and the normal pressure at the operating temperature of the polycondensation reactor in order to maintain the non-alcoholic polar organic matter in liquid state.

[0044] Preferably, the residence time of the material in the polycondensation reactor is 1-3 h, for example, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 1.9 h, 2 h, 2.4 h, 2.6 h or 2.8 h, etc.

[0045] Preferably, the mass percentage of polycarbonate in the material flowing out of the discharge port of the polycondensation reactor is 5-20%, for example, 6%, 8%, 10%, 12%, 14%, 16% or 18%, etc.

[0046] Preferably, the viscosity of the material flowing out of the discharge port of the polycondensation reactor at the operating temperature of the polycondensation reactor is ≤10Pa·S, for example, 1Pa·S, 2Pa·S, 3Pa·S, 4Pa·S, 5Pa·S, 6Pa·S, 7Pa·S, 8Pa·S or 9Pa·S, etc.

[0047] In the present invention, the viscosity of the material flowing out of the discharge port of the polycondensation reactor and the mass percentage of polycarbonate in the material flowing out of the discharge port of the polycondensation reactor can be adjusted by the flow rate of non-alcohol polar organic matter added to the polycondensation reactor. The viscosity of the material flowing out of the discharge port of the polycondensation reactor at the operating temperature of the polycondensation reactor is ≤10Pa·S. The viscosity in the polycondensation reactor is relatively small (less than 10Pa·S), which is conducive to the diffusion of phenol from the polycarbonate melt. The extraction rate of phenol by non-alcohol polar organic matter is much greater than the diffusion rate of phenol. Therefore, it is necessary to reduce the viscosity of the system to facilitate the internal diffusion of phenol.

[0048] Preferably, the feed inlet pressure of the liquid-liquid cyclone is ≥2MpaG, for example, 2.5MpaG, 3MpaG, 3.5MpaG, 4MpaG, 4.5MpaG, 5MpaG, 5.5MpaG, 6MpaG or 6.5MpaG, etc.

[0049] In the present invention, the reactor discharge pump needs to have a higher head to ensure that the feed port pressure of the liquid-liquid cyclone is ≥2MpaG. The reason is that in order to completely separate the materials at the discharge port of the polycondensation reactor, sufficient head is required to be converted into cyclone speed to increase the feed port pressure of the liquid-liquid cyclone, thereby transferring all the polycarbonate to the heavy phase material.

[0050] Preferably, the equipment for the polycondensation reaction comprises a first polycondensation reactor and a second polycondensation reactor, the first polycondensation reactor is connected to a first reactor discharge pump, and the second polycondensation reactor is connected to a second reactor discharge pump.

[0051] Preferably, the equipment of the liquid-liquid separation process comprises a first liquid-liquid cyclone and a second liquid-liquid cyclone, the first liquid-liquid cyclone is connected to the first reactor discharge pump, and the second liquid-liquid cyclone is connected to the second reactor discharge pump.

[0052] Preferably, the operating temperature of the first polycondensation reactor is 160-185°C (e.g., 162°C, 165°C, 170°C, 175°C, 180°C or 183°C, etc.), and the operating temperature of the second polycondensation reactor is 170-195°C (e.g., 172°C, 175°C, 180°C, 185°C, 190°C or 193°C, etc.).

[0053] In the present invention, the equipment for the polycondensation reaction includes a first polycondensation reaction unit and a second polycondensation reaction unit, which is helpful to improve the number average molecular weight of the prepared polycarbonate. The reason is that the polycondensation reaction will produce small molecular phenol. Although the present invention uses non-alcohol polar organic matter to extract the phenol generated by the polycondensation reaction, due to the limitation of extraction equilibrium, phenol will also reach equilibrium in the polycarbonate melt and the liquid phase of the non-alcohol polar organic matter. Therefore, in order to further improve the number average molecular weight of the product polycarbonate, the phenol generated by the polycondensation reaction is further extracted again with fresh non-alcohol polar organic matter in the second scaling reactor, so that the polycondensation reaction can be further carried out.

[0054] Preferably, the head of the discharge pump of the second reactor is greater than the head of the discharge pump of the first reactor.

[0055] In the present invention, the head of the discharge pump of the second reactor is greater than that of the discharge pump of the first reactor because the discharge pump of the second reactor needs to introduce the heavy phase material into the first flash pipeline under pressure, thereby absorbing heat and vaporizing while reducing the pressure.

[0056] Compared with the prior art, the present invention has the following beneficial effects:

[0057] The present invention adds non-alcoholic polar organic matter to extract phenol generated by the polycondensation reaction during the polycondensation reaction of polycarbonate preparation, so that the polycondensation reaction is carried out under low temperature and positive pressure conditions, and the prepared polycarbonate has the characteristics of high number average molecular weight, low yellowness index and high quality. The number average molecular weight of the polycarbonate prepared by the preparation method of low temperature positive pressure synthesis polycarbonate is 14500-22000, and the yellowness index (YI value) is 1.2-2.5; preferably, the number average molecular weight of the polycarbonate prepared by the preparation method of low temperature positive pressure synthesis polycarbonate is 18000-22000, and the yellowness index (YI value) is 1.2-1.3. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 A schematic diagram of the structure of the device used in the method for preparing polycarbonate by low-temperature positive pressure synthesis provided in Example 1;

[0059] Among them, R1-first polycondensation reactor; R2-first reactor discharge pump; R3-first liquid-liquid cyclone; B1-second polycondensation reactor; B2-second reactor discharge pump; B3-second liquid-liquid cyclone; B4-first flash pipeline; B5-second flash pipeline; B6-flash devolatilization tank; B7-extruder; B8-extruder vacuum pump; B9-flash devolatilization tank vacuum pump; B10-first distillation tower; B11-first distillation tower top condenser; B12-first distillation tower reboiler; B13-separation discharge pump; B14-second distillation tower; B15-second distillation tower top condenser; B16-second distillation tower reboiler; B17-non-alcohol polar organic circulation pump; A1-flash section; A2-extrusion section; A3-separation and recovery section;

[0060] S1 is the stream of the ester exchange material flowing into the first polycondensation reactor R1; S2 is the stream of the material flowing out of the discharge port of the first polycondensation reactor R1; S3 is the stream of the material flowing into the first liquid-liquid cyclone R3; S4 is the stream of the material flowing into the second polycondensation reactor B1; S5 is the stream of the material flowing out of the discharge port of the second polycondensation reactor B1; S6 is the stream of the material flowing into the second liquid-liquid cyclone B3; S7 is the stream of the material flowing into the first flash pipe B4; S8 is the stream of the material flowing into the extruder B7; S9 is the stream of the product polycarbonate material flowing out of the extruder B7; S10 is the stream discharged by the vacuum pump gas; S11 is the gas flashed out of the flash devolatilizer B6; S12 is the stream of the light phase material flowing out of the first liquid-liquid cyclone R3 and the second liquid-liquid cyclone B3; S13 is the stream discharged from the top of the first distillation tower B10; S14 is the stream of phenol flowing out of the second distillation tower B14; S15 is the stream of non-alcohol polar organic matter flowing out of the non-alcohol polar organic matter circulation pump B17; S16 is the stream of the added non-alcohol polar organic matter; S17 is the stream of non-alcohol polar organic matter flowing into the first polycondensation reactor R1; S18 is the stream of non-alcohol polar organic matter flowing into the second polycondensation reactor B1;

[0061] Figure 2 A schematic diagram of the structure of the device used in the method for preparing polycarbonate by low-temperature positive pressure synthesis provided in Example 2;

[0062] Among them, B1-polycondensation reactor; B2-reactor discharge pump; B3-liquid-liquid cyclone; B4-first flash pipeline; B5-second flash pipeline; B6-flash devolatilization tank; B7-extruder; B8-extruder vacuum pump; B9-flash devolatilization tank vacuum pump; B10-first distillation tower; B11-first distillation tower top condenser; B12-first distillation tower reboiler; B13-separation discharge pump; B14-second distillation tower; B15-second distillation tower top condenser; B16-second distillation tower reboiler; B17-third distillation tower; B18-third distillation tower top condenser; B19-third distillation tower reboiler; B20-non-alcohol polar organic circulation pump; A1-flash section; A2-extrusion section; A3-separation and recovery section;

[0063] S1 is the stream of the ester exchange material flowing into the polycondensation reactor B1; S2 is the stream of the material flowing out of the discharge port of the polycondensation reactor B1; S3 is the stream of the material flowing into the liquid-liquid cyclone B3; S4 is the stream of the material flowing into the first flash pipeline B4; S5 is the stream of the material flowing into the extruder B7; S6 is the stream of the product polycarbonate material flowing out of the extruder B7; S7 is the gas discharged from the vacuum pump; S8 is the flash devolatilization tank B6 flash stream. The gas discharged from the evaporation; S9 is the stream of the light phase material discharged from the liquid-liquid cyclone B3; S10 is the stream discharged from the top of the first distillation tower B10; S11 is the stream of phenol flowing out of the third distillation tower B17; S12 is the stream of non-alcohol polar organic matter flowing out of the non-alcohol polar organic matter circulation pump B20; S13 is the stream of non-alcohol polar organic matter added; S14 is the stream of non-alcohol polar organic matter added to the polycondensation reactor;

[0064] Figure 3 A schematic diagram of the structure of the device used in the method for preparing polycarbonate by low-temperature positive pressure synthesis provided in Example 3;

[0065] Among them, B1-polycondensation reactor; B2-reactor discharge pump; B3-liquid-liquid cyclone; B4-first flash pipeline; B5-second flash pipeline; B6-flash devolatilization tank; B7-extruder; B8-extruder vacuum pump; B9-flash devolatilization tank vacuum pump; B10-first distillation tower; B11-first distillation tower top condenser; B12-first distillation tower reboiler; B13-separation discharge pump; B14-second distillation tower; B15-second distillation tower top condenser; B16-second distillation tower reboiler; B17-non-alcohol polar organic circulation pump; A1-flash section; A2-extrusion section; A3-separation and recovery section;

[0066] S1 is the stream of the ester exchange material flowing into the polycondensation reactor B1; S2 is the stream of the material flowing out of the discharge port of the polycondensation reactor B1; S3 is the stream of the material flowing into the liquid-liquid cyclone B3; S4 is the stream of the material flowing into the first flash pipeline B4; S5 is the stream of the material flowing into the extruder B7; S6 is the stream of the product polycarbonate material flowing out of the extruder B7; S7 is the gas discharged from the vacuum pump; S8 is the flash evaporation gas discharged from the flash devolatilizer B6 The outflowing gas component; S9 is the stream of the light phase material outflowing from the liquid-liquid cyclone B3; S10 is the stream discharged from the top of the first distillation tower B10; S11 is the stream of phenol outflowing from the second distillation tower B14; S12 is the stream of non-alcohol polar organic matter outflowing from the non-alcohol polar organic matter circulation pump B17; S13 is the stream of non-alcohol polar organic matter added; S14 is the stream of non-alcohol polar organic matter added to the polycondensation reactor;

[0067] Figure 4 A schematic structural diagram of a device used in the method for preparing polycarbonate provided in Comparative Example 1;

[0068] Among them, R1-first polycondensation reactor; R2-first reactor discharge pump; B1-second polycondensation reactor; B2-second reactor discharge pump; B3-extruder; B4-extruder vacuum pump; B5-first reactor primary condenser; B6-first reactor secondary condenser; B7-second reactor primary condenser; B8-second reactor secondary condenser; B9-phenol recovery pump; B10-first polycondensation reactor vacuum pump; B11-second polycondensation reactor vacuum pump; B12-first distillation tower; B13-first distillation tower reboiler; B14-first distillation tower top condenser; B15-separation discharge pump; B16-second distillation tower; B17-second distillation tower reboiler; B18-second distillation tower top condenser; A1-extrusion section; A2-separation recovery section;

[0069] S1 is the stream of the ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and bisphenol A flowing into the first polycondensation reactor R1; S2 is the stream of the material flowing out of the discharge port of the first polycondensation reactor R1; S3 is the stream of the material flowing into the second polycondensation reactor B1; S4 is the stream of the material flowing out of the discharge port of the second polycondensation reactor B1; S5 is the stream of the material flowing into the extruder B3; S6 is the stream of the product polycarbonate material flowing out of the extruder B3; S7 is the gas discharged from the vacuum pump; S8 is the gas discharged from the vacuum pump of the first polycondensation reactor and the vacuum pump of the second polycondensation reactor; S9 is the condensate of the vacuum pump of the first polycondensation reactor and the vacuum pump of the second polycondensation reactor; S10 is the stream discharged from the top of the first distillation tower B10; S11 is the stream of phenol flowing out of the second distillation tower B16; S12 is the stream discharged from the bottom of the second distillation tower B16. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0071] Example 1

[0072] This embodiment provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, and the structural schematic diagram of the device used is as follows: Figure 1 As shown, the device used includes a first polycondensation reactor R1, a first reactor discharge pump R2, a first liquid-liquid cyclone R3, a second polycondensation reactor B1, a second reactor discharge pump B2, a second liquid-liquid cyclone B3, a first flash pipeline B4, a second flash pipeline B5, a flash devolatilization tank B6, an extruder B7, an extruder vacuum pump B8, a flash devolatilization tank vacuum pump B9, a first distillation tower B10, a first distillation tower top condenser B11, a first distillation tower reboiler B12, and a separation discharge pump B13; a second distillation tower B14, a second distillation tower top condenser B15, a second distillation tower reboiler B16, and a non-alcohol polar organic matter circulation pump B17.

[0073] The preparation method comprises the following steps:

[0074] The molar ratio is 1.06:1:2×10 -6 Diphenyl carbonate, bisphenol A and a catalyst for ester exchange reaction (tetramethylammonium hydroxide) are mixed, and then passed through three esterification reactors in sequence to carry out ester exchange reaction, the temperatures of the three esterification reactors passed in sequence are 190° C., 200° C. and 220° C., respectively, the pressures are 40 KPaA, 10 KPaA and 3 KPaA, respectively, and the residence times are 90 min, 70 min and 80 min, respectively, to obtain an ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and bisphenol A.

[0075] The above-mentioned transesterification material and non-alcoholic polar organic matter (acetophenone) are added to the first polycondensation reactor R1, and then sequentially pass through the first reactor discharge pump R2 and the first liquid-liquid cyclone R3. The light phase material produced by the first liquid-liquid cyclone R3 enters the separation and recovery section (A3), and the heavy phase material (S4) and the catalyst for the polycondensation reaction (cerium acetylacetonate) are added to the second polycondensation reactor B1. The molar ratio of the catalyst for the polycondensation reaction (cerium acetylacetonate) to the diphenyl carbonate and bisphenol A added in the above-mentioned transesterification reaction is 5×10 -6:1.06:1, the material (S5) flowing out of the second polycondensation reactor B1 passes through the second reactor discharge pump B2 and the second liquid-liquid cyclone B3 in sequence, the light phase material produced by the second liquid-liquid cyclone B3 enters the separation and recovery device, the heavy phase material (S7) enters the first flash pipeline B4, the second flash pipeline B5 and the flash devolatilization tank B6 for flash evaporation, the gas component (S11) at the top of the flash devolatilization tank B6 enters the separation and recovery section A3 through the flash devolatilization tank vacuum pump B9, the material (S8) at the bottom of the flash devolatilization tank B6 enters the extruder B7, and is extruded to obtain the polycarbonate.

[0076] The light phase material (S12) flowing out of the liquid-liquid cyclone and the gas component (S11) obtained by flash evaporation are separated by separation and recovery section A3, and distilled to obtain phenol (S14) and non-alcohol polar organic matter (S15). The non-alcohol polar organic matter is returned to the first polycondensation reactor R1 again through the non-alcohol polar organic matter circulation pump B17.

[0077] The temperature of the transesterification material (S1) obtained by the transesterification reaction of diphenyl carbonate and bisphenol A is 220° C., and the composition is shown in Table 1 below.

[0078] Table 1

[0079]

[0080]

[0081] The number average molecular weight of the oligomer is 1500.

[0082] The operating temperature of the first polycondensation reactor R1 is 180°C and the pressure is normal pressure (the saturated vapor pressure of phenylacetone at 180°C is -0.064MPaG and the density is 870kg / m 3 ), the residence time of the material is 1.5h, the operating temperature of the second polycondensation reactor B1 is 190°C, and the pressure is normal pressure (the saturated vapor pressure of phenylacetone at 190°C is -0.05MPaG, and the density is 860kg / m 3 ), the residence time of the material is 1.5h, the first flash pipe B4 and the second flash pipe B5 are 300m long inner pipes with DN40 jacket pipes, the first flash pipe B4 is 200m long and the jacket is heated by 2.5MPaG steam, the second flash pipe B5 is 100m long and is heated by heat transfer oil, and the temperature of the heat transfer oil is 320℃.

[0083] The flow of materials in the structure of the device used is shown in Table 2 below.

[0084] Table 2

[0085]

[0086] In Table 2, “-” means that the result was not measured.

[0087] The viscosity of the material and the content of polycarbonate in the streams S2 and S3 are the same, and the viscosity of the material and the content of polycarbonate in the streams S5 and S6 are the same.

[0088] Example 2

[0089] This embodiment provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, and the structural schematic diagram of the device used is as follows: Figure 2 As shown, the device used includes a polycondensation reactor B1, a reactor discharge pump B2, a liquid-liquid cyclone B3, a first flash pipeline B4, a second flash pipeline B5, a flash devolatilization tank B6, an extruder B7, an extruder vacuum pump B8, a flash devolatilization tank vacuum pump B9, a first distillation tower B10, a first distillation tower top condenser B11, a first distillation tower reboiler B12, and a separation discharge pump B13; a second distillation tower B14, a second distillation tower top condenser B15, a second distillation tower reboiler B16, a third distillation tower B17, a third distillation tower top condenser B18, a third distillation tower reboiler B19, and a non-alcohol polar organic matter circulation pump B20.

[0090] The preparation method comprises the following steps:

[0091] The molar ratio is 1.05:0.2:0.8:1.3×10 -6 Diphenyl carbonate, bisphenol A, isosorbide and a catalyst (cesium carbonate) are mixed, and then passed through three esterification reactors in sequence to carry out an ester exchange reaction, the temperatures of the three esterification reactors passed in sequence are 180° C., 185° C. and 190° C., the pressures are 35 KPaA, 10 KPaA and 3 KPaA, and the residence times are 70 min, 70 min and 80 min, respectively, to obtain an ester exchange material obtained by the ester exchange reaction of diphenyl carbonate, bisphenol A and isosorbide.

[0092] The above-mentioned ester exchange material and non-alcoholic polar organic matter (dimethylformamide) are added to the polycondensation reactor B1, and then pass through the reactor discharge pump B2 and the liquid-liquid cyclone B3 in sequence. The light phase material (S9) produced by the liquid-liquid cyclone B3 enters the separation and recovery section (A3), and the heavy phase material (S4) enters the first flash pipeline B4, the second flash pipeline B5 and the flash devolatilization tank B6 for flash evaporation. The gas component (S8) at the top of the flash devolatilization tank B6 enters the separation and recovery section (A3) through the flash devolatilization tank vacuum pump B9. The material (S8) at the bottom of the flash devolatilization tank B9 enters the extruder B7 for extrusion to obtain the polycarbonate.

[0093] The light phase material (S9) flowing out of the liquid-liquid cyclone and the gas component (S8) obtained by flash evaporation are separated by separation and recovery section (A3) and distilled to obtain phenol (S11) and non-alcohol polar organic matter (S12). The non-alcohol polar organic matter is returned to the polycondensation reactor B1 again through the non-alcohol polar organic matter circulation pump B20.

[0094] The temperature of the transesterification material (S1) obtained by the transesterification reaction of diphenyl carbonate, bisphenol A and isosorbide is 200° C. and the composition is shown in Table 3 below.

[0095] Table 3

[0096]

[0097] The number average molecular weight of the polycarbonate oligomer is 7500.

[0098] The operating temperature of the polycondensation reactor B1 is 185°C and the pressure is 0.25 MPaG (the saturated vapor pressure of dimethylformamide at 185°C is 0.129 MPaG and the density is 780 kg / m 3 ), the residence time of the material is 1.5h, the first flash pipe B4 and the second flash pipe B5 are 250m long inner pipes with DN40 jacket pipes, the first flash pipe B4 is 150m long and the jacket is heated by 2.5MPaG steam, the second flash pipe B5 is 100m long and is heated by heat transfer oil, and the temperature of the heat transfer oil is 320℃.

[0099] The flow of materials in the structure of the device used is shown in Table 4 below.

[0100] Table 4

[0101]

[0102]

[0103] In Table 4, “-” means that the result was not measured.

[0104] The viscosity and polycarbonate content of the materials in the streams S2 and S3 are the same.

[0105] Example 3

[0106] This embodiment provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, and the structural schematic diagram of the device used is as follows: Figure 3As shown, the device used includes a polycondensation reactor B1, a reactor discharge pump B2, a liquid-liquid cyclone B3, a first flash pipeline B4, a second flash pipeline B5, a flash devolatilization tank B6, an extruder B7, an extruder vacuum pump B8, a flash devolatilization tank vacuum pump B9, a first distillation tower B10, a first distillation tower top condenser B11, a first distillation tower reboiler B12, and a separation discharge pump B13; a second distillation tower B14, a second distillation tower top condenser B15, a second distillation tower reboiler B16, and a non-alcohol polar organic matter circulation pump B17.

[0107] The preparation method comprises the following steps: mixing the mixture in a molar ratio of 1.06:0.05:0.95:5×10 -6 The diphenyl carbonate, bisphenol A, the fluorene-containing dihydroxy compound as shown in formula I and the catalyst (sodium bicarbonate) are mixed and sequentially passed through three esterification reactors to carry out ester exchange reaction. The temperatures of the three esterification reactors sequentially passed through are 180° C., 185° C. and 195° C., respectively, the pressures are 35 KPaA, 15 KPaA and 5 KPaA, respectively, and the residence times are 60 min, 70 min and 90 min, respectively, to obtain an ester exchange material obtained by the ester exchange reaction of diphenyl carbonate, bisphenol A and the fluorene-containing dihydroxy compound as shown in formula I.

[0108]

[0109]

[0110] The above-mentioned ester exchange material and non-alcoholic polar organic matter (diethylene glycol butyl ether) are added to the polycondensation reactor B1, and then pass through the reactor discharge pump B2 and the liquid-liquid cyclone B3 in sequence. The light phase material (S9) produced by the liquid-liquid cyclone B3 enters the separation and recovery section (A3), and the heavy phase material (S4) enters the first flash pipeline B4, the second flash pipeline B5 and the flash devolatilization tank B6 for flash evaporation. The gas component (S8) at the top of the flash devolatilization tank B6 enters the separation and recovery section (A3) through the flash devolatilization tank vacuum pump B9, and the material (S8) at the bottom of the flash devolatilization tank B9 enters the extruder B7 for extrusion to obtain the polycarbonate.

[0111] The light phase material (S9) flowing out of the liquid-liquid cyclone and the gas component (S8) obtained by flash evaporation are separated by separation and recovery section (A3) and distilled to obtain phenol (S11) and non-alcohol polar organic matter (S12). The non-alcohol polar organic matter is returned to the polycondensation reactor B1 again through the non-alcohol polar organic matter circulation pump B17.

[0112] The temperature of the ester exchange material (S1) obtained by the ester exchange reaction of diphenyl carbonate, bisphenol A and the fluorene-containing dihydroxy compound shown in Formula I is 205° C., and the composition is shown in Table 5 below.

[0113] Table 5

[0114]

[0115] The number average molecular weight of the polycarbonate oligomer is 8600.

[0116] The operating temperature of the polycondensation reactor B1 is 190° C. and the pressure is normal pressure (the saturation pressure of diethylene glycol butyl ether at 190° C. is -0.0677 MPaG and the density is 806 kg / m 3 ), the residence time of the material is 1.5h, the first flash pipe B4 and the second flash pipe B5 are 250m long inner pipes with DN40 jacket pipes, the first flash pipe B4 is 150m long and the jacket is heated by 2.5MPaG steam, the second flash pipe B5 is 100m long and is heated by heat transfer oil, and the temperature of the heat transfer oil is 320℃.

[0117] The flow of materials in the structure of the device used is shown in Table 6 below.

[0118] Table 6

[0119]

[0120] In Table 6, “-” means that the result was not measured.

[0121] The viscosity and polycarbonate content of the materials in the streams S2 and S3 are the same.

[0122] Example 4

[0123] This embodiment provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, which differs from Example 3 only in that diethylene glycol butyl ether is replaced by diethylene glycol butyl ether and polyethylene glycol (number average molecular weight is 400) in a mass ratio of 9:1; S13 is the stream of the added diethylene glycol butyl ether and polyethylene glycol materials.

[0124] The flow of materials in the structure of the device used is shown in Table 7 below.

[0125] Table 7

[0126]

[0127] In Table 7, “-” means that the result was not measured.

[0128] The viscosity and polycarbonate content of the materials in the streams S2 and S3 are the same.

[0129] The rest is the same as Example 3.

[0130] Example 5

[0131] The present embodiment provides a method for preparing polycarbonate by low-temperature positive pressure synthesis, which differs from Embodiment 3 only in that the flow rate of stream S14 is adjusted to 1000 kg / h, the viscosity of the materials in streams S2 and S3 is the same as the content of polycarbonate, the mass percentage of polycarbonate in the materials (S2 and S3) flowing out of the discharge port of the polycondensation reactor is 50%, and the viscosity of the materials (S2 and S3) flowing out of the discharge port of the polycondensation reactor at 190°C is 15.8 Pa·S.

[0132] The flow of materials in the structure of the device used is shown in Table 8 below.

[0133] Table 8

[0134]

[0135]

[0136] In Table 8, “-” means that the result was not measured.

[0137] The rest is the same as Example 3.

[0138] Comparative Example 1

[0139] This comparative example provides a method for preparing polycarbonate, and the structural schematic diagram of the device used is as follows Figure 4 As shown, the device used includes a first polycondensation reactor R1, a first reactor discharge pump R2, a second polycondensation reactor B1, a second reactor discharge pump B2, an extruder B3, an extruder vacuum pump B4, a first reactor primary condenser B5, a first reactor secondary condenser B6, a second reactor primary condenser B7, a second reactor secondary condenser B8, a phenol recovery pump B9, a first polycondensation reactor vacuum pump B10, a second polycondensation reactor vacuum pump B11, a first distillation tower B12, a first distillation tower reboiler B13, a first distillation tower top condenser B14, a separation discharge pump B15, a second distillation tower B16, a second distillation tower reboiler B17, and a second distillation tower top condenser B18.

[0140] The preparation method comprises the following steps:

[0141] The molar ratio is 1.06:1:2×10 -6 Diphenyl carbonate, bisphenol A and a catalyst for ester exchange reaction (tetramethylammonium hydroxide) are mixed, and then passed through three esterification reactors in sequence to carry out ester exchange reaction, the temperatures of the three esterification reactors passed in sequence are 190° C., 200° C. and 220° C., respectively, the pressures are 40 KPaA, 10 KPaA and 3 KPaA, respectively, and the residence times are 90 min, 70 min and 80 min, respectively, to obtain an ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and bisphenol A.

[0142] The above transesterification material is added to the first polycondensation reactor R1, and then passed through the first reactor discharge pump R2, and added to the second polycondensation reactor B1 with the polycondensation reaction catalyst (cerium acetylacetonate). The molar ratio of the polycondensation reaction catalyst (cerium acetylacetonate) to the diphenyl carbonate and bisphenol A added in the above transesterification reaction is 5×10 -6 :1.06:1, the material (S4) flowing out of the second polycondensation reactor B1 enters the extruder B3 through the second reactor discharge pump B2, and is extruded to obtain the polycarbonate. The first polycondensation reactor vacuum pump B10 and the second polycondensation reactor vacuum pump B11 maintain the vacuum environment of the first polycondensation reactor R1 and the second polycondensation reactor B1.

[0143] The temperature of the transesterification material (S1) obtained by the transesterification reaction of diphenyl carbonate and bisphenol A is 220° C., and the composition is shown in Table 9 below.

[0144] Table 9

[0145] composition Oligomer Diphenyl carbonate Bisphenol A phenol Impurities Content (wt%) 93.3 3.5 2.8 0.23 0.17

[0146] The number average molecular weight of the oligomer is 1500.

[0147] The operating temperature of the first polycondensation reactor R1 is 260°C, the pressure is 0.6 KPaA, and the material residence time is 60 min. The operating temperature of the second polycondensation reactor B1 is 290°C, the pressure is 0.05 KPaA, and the material residence time is 60 min.

[0148] The flow of materials in the structure of the device used is shown in Table 10 below.

[0149] Table 10

[0150]

[0151]

[0152] Performance Testing

[0153] The following performance tests were performed on the polycarbonate prepared by the preparation methods of the polycarbonate provided in the examples and comparative examples.

[0154] (1) Number average molecular weight: A gel permeation chromatograph, Model 150C from Waters, was used. The polycarbonate sample was first vacuum dried, and then a 0.3 wt% polycarbonate solution was prepared with tetrahydrofuran as solvent. The sample was filtered through a 0.5 μm filter membrane before injection. A high-efficiency PS gel chromatographic column (104-103-linear three columns in series) was used, the temperature was 25°C, the injection volume was 40 mL, and the average number average molecular weight was obtained after data processing after the test.

[0155] (2) Yellowness index (YI value): A CS-820N desktop spectrophotometer produced by Hangzhou Caipu Company was used. The test mode was transmission mode, an 18 mm aperture was used, the irradiation light source was a C-light cold light source, the irradiation angle was 2°, and a single sample was tested 3 times to obtain the average value. The thickness of the tested polycarbonate sheet was 1 mm.

[0156] The test results are shown in Table 11.

[0157] Table 11

[0158]

[0159]

[0160] According to the test results in Table 11, the number average molecular weight of the polycarbonate prepared by the method for preparing polycarbonate synthesized at low temperature and positive pressure provided in Examples 1-5 is 14500-22000, and the yellowness index (YI value) is 1.2-2.5. The number average molecular weight of the polycarbonate prepared by the method for preparing polycarbonate synthesized at low temperature and positive pressure provided in Examples 1-4 is 18000-22000, and the yellowness index (YI value) is 1.2-1.3.

[0161] Compared with Example 1, if diethylene glycol butyl ether is replaced with diethylene glycol butyl ether and polyethylene glycol in a mass ratio of 9:1 (Example 4), the number average molecular weight of the obtained polycarbonate is increased. The reason is that polyethylene glycol has a strong solubility for phenols, and the addition of polyethylene glycol has a good effect on extracting phenol, thereby increasing the number average molecular weight of the obtained polycarbonate, which proves that the addition of polyethylene glycol to prepare polycarbonate is more effective.

[0162] Compared with Example 1, if the viscosity of the material flowing out of the discharge port of the polycondensation reactor is too large (Example 5), the number average molecular weight of the obtained polycarbonate is reduced, and the yellowness index (YI value) is reduced. The reason is that the viscosity of the material at the discharge port of the polycondensation reactor is too large (increased to 15.8 Pa·S), which is not conducive to the diffusion of phenol from the polymer melt. In addition, the amount of diethylene glycol butyl ether is also small, and the ability to dissolve phenol is relatively reduced. Therefore, the degree of polymerization of the obtained polycarbonate is reduced, and the number average molecular weight is reduced. The number average molecular weight of the polycarbonate is only 14500. In addition, at the liquid-liquid cyclone, due to the small amount of liquid and high viscosity, more polycarbonate will enter the separation and recovery device in the form of a light phase. Since the number average molecular weight of the obtained polycarbonate is low, a higher temperature is required in the flash evaporation and extrusion process to effectively remove small molecules, and the yellowness index (YI value) of the obtained polycarbonate will become higher.

[0163] Compared with Example 1, the polycarbonate prepared by the conventional polycarbonate preparation method (Comparative Example 1) has a lower number average molecular weight and a higher yellowness index (YI value).

[0164] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing polycarbonate by low temperature positive pressure synthesis, characterized in that: The preparation method comprises the following steps: (1) mixing the ester exchange material obtained by the ester exchange reaction of diphenyl carbonate and dihydroxy compound with non-alcoholic polar organic matter, carrying out polycondensation reaction, and obtaining light phase material and heavy phase material through liquid-liquid separation process; (2) flash evaporating and extruding the heavy phase material of step (1) to obtain the polycarbonate; The non-alcoholic polar organic matter includes any one of formamide, diethylene glycol butyl ether, ethylene glycol butyl ether, propiophenone or glutaraldehyde, or a combination of at least two thereof.

2. The preparation method according to claim 1, characterized in that: The dihydroxy compound includes any one of bisphenol A, isomannide, isoidide, isosorbide, 1,4-cyclohexanedimethanol or a fluorene-containing dihydroxy compound or a combination of at least two thereof.

3. The preparation method according to claim 1, characterized in that: The molar ratio of the diphenyl carbonate to the dihydroxy compound is 1:1-1.

1.

4. The preparation method according to claim 1, characterized in that: The mixing in step (1) further comprises adding polyethylene glycol for mixing; Taking the total mass of the non-alcoholic polar organic matter and the polyethylene glycol as 100%, the mass percentage of the polyethylene glycol is 0-10%.

5. The preparation method according to claim 4, characterized in that: The number average molecular weight of the polyethylene glycol is ≤400.

6. The preparation method according to claim 1, characterized in that: The equipment for the polycondensation reaction in step (1) comprises at least one polycondensation reactor, and the polycondensation reactor is connected to a reactor discharge pump.

7. The preparation method according to claim 1, characterized in that: The equipment of the liquid-liquid separation process comprises at least one liquid-liquid cyclone, and the liquid-liquid cyclone is connected to the reactor discharge pump.

8. The preparation method according to claim 7, characterized in that: The light phase substance flowing out of the liquid-liquid cyclone and the gas component obtained by flash evaporation are separated by rectification to obtain phenol and non-alcohol polar organic matter.

9. The preparation method according to claim 1, characterized in that: The flash evaporation equipment comprises a first flash evaporation pipeline, a second flash evaporation pipeline and a flash evaporation devolatilization tank.

10. The preparation method according to claim 9, characterized in that: The first flash pipeline is heated by medium-pressure steam, and the second flash pipeline is heated by heat-conducting oil.

11. The preparation method according to claim 9, characterized in that: The heating temperature of the first flash pipe is less than or equal to the heating temperature of the second flash pipe.

12. The preparation method according to claim 8, characterized in that: The distillation separation equipment includes a first distillation tower and a second distillation tower.

13. The preparation method according to claim 8, characterized in that: The distillation separation equipment also includes a third distillation tower.

14. The preparation method according to claim 9, characterized in that: The operating temperatures of the polycondensation reactor and the first flash conduit are each independently ≤ 200°C.

15. The preparation method according to claim 6, characterized in that: The pressure of the polycondensation reactor is ≥ the larger value of the saturated vapor pressure of non-alcoholic polar organic matter and normal pressure at the operating temperature of the polycondensation reactor.

16. The preparation method according to claim 6, characterized in that: The mass percentage of polycarbonate in the material flowing out of the discharge port of the polycondensation reactor is 5-20%.

17. The preparation method according to claim 6, characterized in that: The viscosity of the material flowing out of the discharge port of the polycondensation reactor at the operating temperature of the polycondensation reactor is ≤10 Pa·S.

18. The preparation method according to claim 7, characterized in that: The feed port pressure of the liquid-liquid cyclone is ≥2MpaG.

19. The preparation method according to claim 1, characterized in that: The polycondensation reaction equipment comprises a first polycondensation reactor and a second polycondensation reactor, wherein the first polycondensation reactor is connected to a first reactor discharge pump, and the second polycondensation reactor is connected to a second reactor discharge pump.

20. The preparation method according to claim 7, characterized in that: The equipment of the liquid-liquid separation process comprises a first liquid-liquid cyclone and a second liquid-liquid cyclone, wherein the first liquid-liquid cyclone is connected to a first reactor discharge pump, and the second liquid-liquid cyclone is connected to a second reactor discharge pump.

21. The preparation method according to claim 19, characterized in that: The operating temperature of the first polycondensation reactor is 160-185°C, and the operating temperature of the second polycondensation reactor is 170-195°C.

22. The preparation method according to claim 19, characterized in that: The head of the discharge pump of the second reactor is greater than the head of the discharge pump of the first reactor.

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