Apparatus and method for preparing liquid crystal polymer

Abstract

The application discloses a preparation device and method of liquid crystal polymer, the device comprises: devolatilization reactor, reheater, polymerization reactor and acylation reactor; the liquid phase outlet of the acylation reactor is communicated with the feeding port of the devolatilization reactor, the gas phase outlet of the acylation reactor, the gas phase outlet of the devolatilization reactor and the gas phase outlet of the polymerization reactor are all communicated with the inlet of the reheater, the outlet of the reheater is communicated with the gas phase inlet of the devolatilization reactor, and the liquid phase outlet of the devolatilization reactor is communicated with the feeding port of the polymerization reactor. The method comprises the following steps: in step 1), after weighing and mixing reactants, acylation reagent and catalyst are added and dissolved to obtain a reaction solution; in step 2), the reaction solution is subjected to acylation reaction in the acylation reactor, devolatilization in the devolatilization reactor and then polycondensation reaction in the polymerization reactor to obtain a polymer melt; and in step 3), the polymer melt is cooled and then crushed and granulated. The application can effectively avoid homopolymerization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer devolatilization devices, and particularly relates to a device and method for preparing liquid crystal polymers. BACKGROUND

[0002] The production of the present liquid crystal polymer (LCP) contains two steps of acylation and polycondensation. The acylation step is to react monomers such as 4-hydroxybenzoic acid with acetic anhydride to convert phenolic hydroxyl into acyloxy, and produce by-product carboxylic acid. The polycondensation step is to react the acyloxy with the carboxyl to generate ester bond, and meanwhile, to remove one molecule of carboxylic acid as by-product. Since the presence of carboxylic acid inhibits the progress of polycondensation reaction, it is necessary to devolatilize the acetylation reactant to remove carboxylic acid. In the acetylation step, in order to maximize the conversion rate of phenolic hydroxyl, slightly more than 1 equivalent of anhydride is often used as the reactant. However, even so, there are still a small amount of unreacted hydroxyl in the reaction mixture. In the existing production process, considering the cost and boiling point, acetic anhydride (acetic anhydride) is generally used as the acylating agent, and acetic acid is removed as a by-product, so it becomes acetylation.

[0003] The devolatilization process of the existing acetylation product generally has the following three kinds:

[0004] The first is to directly heat to make most of the acetic acid volatilize, and introduce acetic acid vapor into a condenser for acetic acid recovery. This method has the advantage of simple device, but also has the following disadvantages. First, the acetic anhydride is removed together, and the conversion rate of the reaction is difficult to further improve. Second, in the simple distillation process, due to the different polymerization activities of different monomers in the reaction mixture, monomer 4-acetyloxybenzoic acid is prone to homopolymerization, and this homopolymerization phenomenon intensifies with the increase of the residence time of the reaction mixture in the temperature range of about 170-220℃, which simultaneously causes significant difficulties in the scale-up of the liquid crystal polymer reactor. In addition, in the simple distillation process, due to the different boiling points of different monomers, different degrees of volatilization are easy to occur, resulting in changes in the molar ratio of monomers in the reaction mixture. This phenomenon often causes problems such as reactor gas path blockage and low molecular weight of the product in the preparation of type I industrialized liquid crystal polymers involving diphenol monomers with lower boiling points and higher polymerization temperatures.

[0005] The second is to remove the volatile by means of rectifying column, in which the reaction mixture is in the column kettle, and the rectifying column is used to selectively separate acetic acid, while retaining acetic anhydride to improve the conversion rate of the reaction. This scheme is mainly to make up for the deficiency of the first scheme in the conversion rate of the reaction, which reduces the volatilization of acetic anhydride by increasing the rectifying section, so as to promote the equilibrium of the acetylation reaction to move in the positive direction. However, due to the reflux of the rectifying column, the requirement for the heating capacity of the reaction kettle is even higher than that of the first scheme, so the problem of homopolymerization is more serious. In addition, due to the change of the composition of the reactants during the rectifying process, the rectifying column often does not reach its highest separation efficiency, and the refluxing acetic acid in the dead volume of the column is also easy to cause the temperature of the column kettle to be difficult to rise in the later stage of rectification.

[0006] The third is to slowly remove the acetic acid after the reaction mixture is pressurized and heated. This scheme is mainly to make up for the deficiency of the above two schemes in the problem of homopolymerization, and the strategy is to heat the reaction mixture without removing or only removing a small amount of acetic acid, so that it is heated to a temperature of 220 DEG C or more, often more than 240 DEG C, and then removed by simple distillation or rectification at high temperature. The main defect of this scheme is that it requires a higher performance of the reactor, which requires the reactor to have a certain pressure resistance, thus increasing the investment cost of the equipment. At the same time, this technology requires the acetic acid to be heated to a high temperature for removal, which increases the energy consumption of the process, and the corrosion of high-temperature acetic acid to the equipment is higher than the previous two schemes. In addition, this technical scheme involves the continuous change of the pressure in the kettle, which has difficulties in the continuous preparation of liquid crystal polyarylate, and is difficult to meet the requirements of continuous preparation of liquid crystal polyarylate.

[0007] Therefore, it is urgent to provide a preparation device and method of liquid crystal polymer to alleviate the homopolymerization phenomenon of acetylation product in the acetic acid removal step of the preparation process of liquid crystal polymer. SUMMARY

[0008] In view of the above-mentioned shortcomings or deficiencies of the prior art, the technical problem to be solved by the present application is to provide a preparation device and method of liquid crystal polymer.

[0009] To solve the above technical problems, the present application realizes the following technical scheme:

[0010] The application provides a liquid crystal polymer preparation device, which comprises a devolatilization reactor, a reheater, at least one polymerization reactor and at least one acylation reactor, a liquid phase outlet of the acylation reactor is communicated with a feeding port of the devolatilization reactor, a gas phase outlet of the acylation reactor, a gas phase outlet of the devolatilization reactor and a gas phase outlet of the polymerization reactor are all communicated with an inlet of the reheater, an outlet of the reheater is communicated with a gas phase inlet of the devolatilization reactor, and a liquid phase outlet of the devolatilization reactor is communicated with a feeding port of the polymerization reactor.

[0011] Further, the liquid crystal polymer preparation device, wherein the devolatilization reactor comprises a reflux section, a rectification section and a stripping section which are sequentially arranged in a shell, a feeding port is arranged between the rectification section and the stripping section, a gas phase outlet is arranged at the upper portion of the reflux section, and a gas phase inlet and a liquid phase outlet are arranged at the lower portion of the stripping section.

[0012] Further, the liquid crystal polymer preparation device, wherein the rectification section comprises a plate tower or a packed tower.

[0013] Further, the liquid crystal polymer preparation device, wherein the device further comprises a dissolving kettle, and an outlet of the dissolving kettle is communicated with a feeding port of the acylation reactor.

[0014] Further, the liquid crystal polymer preparation device, wherein a stirrer is arranged in the acylation reactor and / or the dissolving kettle.

[0015] Further, the liquid crystal polymer preparation device, wherein the device further comprises a condenser and a recovery tank, an inlet of the condenser is communicated with a gas phase outlet of the devolatilization reactor and an inlet of the reheater, and an outlet of the condenser is communicated with the recovery tank.

[0016] The application further provides a liquid crystal polymer preparation method, which adopts the liquid crystal polymer preparation device, and comprises the following steps.

[0017] Step 1) weighing and mixing reactants, then adding an acylation reagent and a catalyst for dissolving to obtain a reaction solution;

[0018] Step 2) performing acylation reaction on the reaction solution in the acylation reactor, then performing devolatilization on the reaction solution in the devolatilization reactor, and then performing polycondensation reaction on the reaction solution in the polymerization reactor to obtain a polymer melt;

[0019] Step 3) cooling and crushing the polymer melt to obtain granules.

[0020] Further, the liquid crystal polymer preparation method, wherein the temperature of the material in the acylation reactor is 100-160 ℃.

[0021] Further, the method for preparing liquid crystal polymer, wherein the temperature of the feed inlet of the devolatilization reactor is 120-180℃.

[0022] Further, the method for preparing liquid crystal polymer, wherein the temperature of the feed inlet of the devolatilization reactor is 120-180℃.

[0023] Compared with the prior art, the present application has the following technical effects:

[0024] The present application utilizes the devolatilization reactor to rapidly devolatilize the reactants. Compared with the prior art, the present application has a shorter residence time in the homopolymerization temperature zone, effectively alleviating the occurrence of homopolymerization. The reboiler is utilized to reheat the acetic acid vapor generated in the acylation reactor and the devolatilization reactor, form superheated acetic acid vapor, and then pass the superheated acetic acid vapor into the devolatilization reactor to continue devolatilization by utilizing the high temperature of the superheated acetic acid vapor. The large gas-phase acetic acid partial pressure is conducive to inhibiting homopolymerization, and also achieves the effect of energy saving and consumption reduction.

[0025] The present application can continuously feed and discharge, and is suitable for a semi-continuous or full-continuous process for preparing liquid crystal polymer. The reaction process of the present application can be carried out at atmospheric pressure. The devolatilization reactor can be made of inert inorganic non-metallic materials such as glass or ceramic, and the construction cost is lower than that of the strategy of using pressurization to retain acetic acid to avoid homopolymerization. The temperature change of the present application mainly occurs in the devolatilization reactor, and the operating temperature of the remaining reaction devices is basically constant. The operation and design are relatively low in difficulty compared with the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments made with reference to the accompanying drawings:

[0027] Figure 1 : Schematic diagram of the preparation device of liquid crystal polymer in an embodiment of the present application;

[0028] Figure 2 : Schematic diagram of the simulation device of the devolatilization reactor in Example 4 of the present application;

[0029] In the figure: dissolving kettle 1, first acylation reactor 2, second acylation reactor 3, devolatilization reactor 4, reflux section 5, rectification section 6, stripping section 7, condenser 8, recovery tank 9, reboiler 10, first steam pump 11, second steam pump 12, polymerization reactor 13, stirring paddle 14, first column section 15, second column section 16, third column section 17, thermometer 18, heat insulation layer 19, straight connector 20, Y-shaped tee connector 21, first injection pump 22, second injection pump 23, and reflux condenser tube 24. DETAILED DESCRIPTION

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] like Figure 1 As shown in one embodiment of this application, a liquid crystal polymer preparation apparatus includes: a devolatilization reactor 4, a reheater 10, at least one polymerization reactor 13, and at least one acylation reactor; the liquid phase outlet of the acylation reactor is connected to the feed inlet of the devolatilization reactor 4, the gas phase outlet of the acylation reactor, the gas phase outlet of the devolatilization reactor 4, and the gas phase outlet of the polymerization reactor 13 are all connected to the inlet of the reheater 10, the outlet of the reheater 10 is connected to the gas phase inlet of the devolatilization reactor 4, and the liquid phase outlet of the devolatilization reactor 4 is connected to the feed inlet of the polymerization reactor 13.

[0032] In this embodiment, the number of acylation reactors is set to two, and the number of polymerization reactors 13 is set to three. Those skilled in the art will be motivated to adapt the number of reactors by increasing or decreasing it. The first acylation reactor 2 and the second acylation reactor 3 are connected in parallel, and the three polymerization reactors 13 are connected in series. The reactants enter from the inlet of the first acylation reactor 2 and the inlet of the second acylation reactor 3. The liquid phase outlet of the first acylation reactor 2 and the liquid phase outlet of the second acylation reactor 3 are connected to the inlet of the devolatilization reactor 4. The gas phase outlets of the first acylation reactor 2, the second acylation reactor 3, and the devolatilization reactor 4 are all connected to the inlet of the reheater 10. The outlet of the reheater 10 is connected to the gas phase inlet of the devolatilization reactor 4. The liquid phase outlet of the devolatilization reactor 4 is connected to the inlet of the polymerization reactor 13, and the gas phase outlet of the polymerization reactor 13 is connected to the inlet of the reheater 10. With the above settings, this embodiment uses devolatilization reactor 4 to rapidly devolatilize the reactants. Compared with the prior art, this embodiment has a shorter residence time in the homopolymerization temperature zone, effectively alleviating the occurrence of homopolymerization. In this embodiment, reheater 10 is used to reheat the acetic acid vapor generated in acylation reactor and devolatilization reactor 4 to form superheated acetic acid vapor, which is then introduced into devolatilization reactor 4. Devolatilization continues using the high temperature of the superheated acetic acid vapor. The partial pressure of gaseous acetic acid is relatively large, which is beneficial to suppressing homopolymerization and also achieves the effect of energy saving and consumption reduction.

[0033] Optionally, a first steam pump 11 is provided between the gas phase outlet of the devolatilization reactor 4 and the inlet of the reheater 10 to facilitate steam flow.

[0034] Optionally, a second steam pump 12 is provided between the gas phase outlet of the polymerization reactor 13 and the inlet of the reheater 10 to facilitate the steam flow.

[0035] In particular, the liquid crystal polymer preparation device further comprises a dissolving kettle 1, the outlet of which is communicated with the feed inlet of the acylation reactor. The dissolving kettle 1 is used for metering, mixing and dissolving the reactant materials.

[0036] In the present embodiment, the outlet of the dissolving kettle 1 is communicated with the feed inlet of the first acylation reactor 2 and the feed inlet of the second acylation reactor 3. The aromatic hydroxyl carboxylic acid, diphenol monomer, acylation reagent and catalyst are weighed and added into the dissolving kettle 1, which mixes the above materials and preheats to prepare a uniform reactant solution. When the polymerization reaction involves an insoluble dicarboxylic acid monomer such as terephthalic acid, it is preferred to directly add the above dicarboxylic acid monomer into the polymerization reactor 13 after the removal of volatile matter in the reaction mixture, so as to avoid the deposition of insoluble terephthalic acid in the removal of volatile matter reactor 4 and the acylation reactor. After the completion of the reactant dissolution, the material is a uniform and clear solution, which flows from the outlet of the dissolving kettle 1 into the feed inlet of the first acylation reactor 2 and the feed inlet of the second acylation reactor 3 to perform the acylation reaction.

[0037] Optionally, the acylation reactor and / or the dissolving kettle 1 is provided with a stirring paddle 14 to facilitate the sufficient reaction of the reactants.

[0038] Preferably, the stirring paddle 14 of the dissolving kettle 1 is a plate-frame type or anchor type stirring paddle 14.

[0039] Optionally, the acylation reactor comprises a batch reactor or a continuous reactor.

[0040] Preferably, the acylation reactor body is a reaction kettle with heat exchange coils, tubes or fins.

[0041] Preferably, the acylation reactor is further provided with a condensing device to condense and recycle the acetic acid for reuse.

[0042] In the present embodiment, the main role of the first acylation reactor 2 and the second acylation reactor 3 is to acylate the monomer with the acid anhydride to convert the phenolic hydroxyl group into acyloxy group. The feature is to set the stirring and heat transfer system for the low viscosity characteristics of the reaction material, and to have greater heat removal capacity relative to the light inner wall of the ordinary polycondensation kettle, i.e. the configuration without built-in heat exchange fins or coils. In order to ensure the continuity of the feed of the devolatilization reactor 4 and the polymerization reactor 13, the acylation reactor adopts the parallel arrangement of the first acylation reactor 2 and the second acylation reactor 3. In order to remove the reaction heat and reduce the devolatilization load of the devolatilization reactor 4, part of the acetic acid can be removed by evaporation in the first acylation reactor 2 and the second acylation reactor 3. However, in order to avoid the occurrence of homopolymerization due to the shift of the balance, the acetic acid removed in the first acylation reactor 2 and the second acylation reactor 3 should not exceed 50% of the acetic acid produced by the acylation reaction. Due to the large nature of the vaporization heat of acetic acid itself, it is difficult to remove all the generated acetic acid by relying on the heat carried by the superheated acetic acid in the polymerization reactor 13, so auxiliary heating, or superheating the feed, or removing a small amount of acetic acid in advance is needed, so the removed acetic acid can be reheated by the first steam pump 11 into the reheater 10 for use.

[0043] Specifically, the liquid crystal polymer preparation device further comprises a condenser 8 and a recovery tank 9; the inlet of the condenser 8 is in communication with the gas phase outlet of the devolatilization reactor 4 and the inlet of the reheater 10, and the outlet of the condenser 8 is in communication with the recovery tank 9.

[0044] In the present embodiment, part of the acetic acid removed by the acylation reactor is condensed by the condenser 8 into the recovery tank 9 for recovery as a byproduct.

[0045] Specifically, the devolatilization reactor 4 comprises a reflux section 5, a rectification section 6 and a stripping section 7 arranged in sequence in the shell; a feed inlet is arranged between the rectification section 6 and the stripping section 7, a gas phase outlet is arranged at the upper part of the reflux section 5, and a gas phase inlet and a liquid phase outlet are arranged at the lower part of the stripping section 7.

[0046] In the present embodiment, the acetylation reaction mixture is fed from the feed inlet of the devolatilization reactor 4, i.e. from the middle of the devolatilization reactor 4, above which is the reflux section 5 and the rectification section 6, and below which is the stripping section 7. The function of the reflux section 5 is to create reflux of acetic acid and control the reflux flow rate so that the acid anhydride and volatile monomers are flushed back. The function of the rectification section 6 is to trap the volatile monomers and heavier components such as acetic anhydride and separate them from the acetic acid. One of the purposes of the rectification section 6 is to reflux the acetic anhydride into the reaction mixture to increase the conversion rate of the phenolic hydroxyl groups in the material. In addition, in processes involving volatile monomers, especially diphenol monomers and volatile catalysts, the rectification section 6 is also used to reflux the above-mentioned materials to avoid the volatilization of the above-mentioned materials from causing the deviation of the reaction catalyst content and the functional group ratio of the monomers. The function of the stripping section 7 is to provide a large enough gas-liquid contact area to quickly devolatilize the reactants without causing a large amount of homopolymerization of the acetylated monomers. The devolatilized monomers after devolatilization flow into the feed inlet of the polymerization reactor 13 through the liquid phase outlet of the devolatilization reactor 4 for condensation reaction.

[0047] Optionally, the rectification section 6 includes but is not limited to a plate column or a packed column.

[0048] Optionally, when the rectification section 6 adopts a plate column, the number of plates is 2-100; preferably, the number of plates of the rectification section 6 is 4-50, such as 25.

[0049] In the present embodiment, considering the corrosiveness of the acetic acid-containing medium, the rectification section 6 adopts a packed column and is used in combination with inert non-metallic packing, such as ceramic rings, glass springs and the like.

[0050] Optionally, the stripping section 7 includes but is not limited to a plate column, a packed column, a falling film reactor, a tubular structure reactor, a column structure reactor or a flat plate structure reactor to increase the surface area for gas-liquid exchange. Of course, those skilled in the art have the motivation to adopt a vertical or inclined arrangement of the tubular structure, column structure or flat plate structure.

[0051] Optionally, when the stripping section 7 adopts a plate column, the number of plates is 2-100; preferably, the number of plates of the stripping section 7 is 5-50, such as 30.

[0052] In the present embodiment, considering the corrosiveness of the acetic acid-containing material, the stripping section 7 adopts a packed column and is used in combination with inert non-metallic packing, such as ceramic rings, glass springs and the like. In addition, the packing is in the form of ring-shaped loose packing with large pores or monolithic structured packing. Under the premise of ensuring that the reaction liquid has sufficient specific surface area when flowing through the stripping section 7, the resistance of the packing layer is controlled to avoid the occurrence of blockage.

[0053] Optionally, the heat acquisition of the devolatilization reactor 4 is through convection heating, conduction heating and / or radiation heating; the convection heating includes but is not limited to heating through the way of inputting heat by high-temperature gas; the conduction heating includes but is not limited to heating through the way of conducting heat oil or electricity on the wall surface; the radiation heating includes but is not limited to using built-in microwave or infrared heating device.

[0054] In the embodiment, the superheated acetic acid vapor is used for convection heating, the acetic acid vapor from the polymerization reactor 13 is introduced into the reheater 10 through the gas phase outlet of the polymerization reactor 13 by the second steam pump 12, and the insufficient part of the flow is supplemented by the first steam pump 11 to transport the acetic acid vapor generated by the devolatilization reactor 4 and the acylation reactor. The mixed acetic acid vapor flows into the reheater 10 to be heated, and the superheated acetic acid vapor with stable temperature and flow is obtained, which flows into the gas phase inlet of the devolatilization reactor 4 through the outlet of the reheater 10.

[0055] Through the above arrangement, the devolatilization reactor 4 quickly removes the volatile matter and increases the material temperature, so that the material quickly reaches the low-acetic acid content and high-temperature polycondensation reaction state, and the homopolymerization phenomenon in the heating process is reduced.

[0056] Optionally, the polymerization reactor 13 includes but is not limited to at least one continuous reactor or batch kettle reactor.

[0057] Preferably, the continuous reactor is a horizontal double-screw continuous reactor.

[0058] In the embodiment, the polymerization reactor 13 uses three continuous reactors, and those skilled in the art are motivated to adaptively increase or decrease the number of settings. In the embodiment, the three continuous reactors are connected in series, and the temperature and vacuum degree of the continuous reactors are gradually increased according to the increasing conversion rate in the reaction. Another role of the polymerization reactor 13 in the embodiment is to provide the required acetic acid vapor for the devolatilization reactor 4.

[0059] In the embodiment, the reaction product obtained by the polymerization reactor 13 is a melt, which is extruded by a melt pump or a screw, and finally cooled by a water tank, broken and granulated.

[0060] Another aspect of the present application also provides a preparation method of liquid crystal polymer, which uses the preparation device of liquid crystal polymer described above, and the method comprises the following steps:

[0061] Step 1) After weighing the reactants, the reactants are mixed, acylation reagent and catalyst are added and dissolved to obtain a reaction solution;

[0062] Step 2) The reaction solution is subjected to acylation reaction in the acylation reactor, devolatilization in the devolatilization reactor 4, and then polycondensation reaction in the polymerization reactor 13 to obtain a polymer melt;

[0063] Step 3) The polymer melt is cooled and broken into granules.

[0064] In this embodiment, the preparation method is directed to thermotropic liquid crystalline polyarylates, especially Type I and Type II liquid crystalline polyarylates.

[0065] Specifically, the reactants are those commonly used in the art for the manufacture of liquid crystalline polyarylates, including: aromatic hydroxycarboxylic acid monomers; or, aromatic hydroxycarboxylic acid monomers, diacid monomers and diphenol monomers. Both of the above-mentioned reactants can be selected by those skilled in the art according to requirements, while adding diacid monomers and diphenol monomers to maintain the balance of the total number of carboxyl groups and the total number of hydroxyl groups.

[0066] Specifically, the aromatic hydroxycarboxylic acid monomers include hydroxybenzoic acid, hydroxynaphthoic acid and / or their isomers.

[0067] Specifically, the diacid monomers include phthalic acid, diphenic acid, naphthalene dicarboxylic acid and / or their isomers.

[0068] Specifically, the diphenol monomers include p-dihydroxybenzene, m-dihydroxybenzene, dihydroxydiphenyl ether, bisphenol A, diphenol and / or their isomers.

[0069] Specifically, the acylating agent includes acid anhydride; preferably, the acylating agent is acetic anhydride.

[0070] Optionally, the catalyst includes metal salts, ionic liquids, sulfonic acids and / or organic bases.

[0071] Optionally, the metal salts include, but are not limited to, zinc salts and potassium salts.

[0072] Specifically, the temperature of the material in the dissolving kettle 1 is less than or equal to 110°C to avoid self-acceleration of the acylation reaction. After the material is completely dissolved, the residence time in the dissolving kettle 1 is not higher than 20 min.

[0073] Specifically, the temperature of the material in the acylation reactor is 100-160°C; preferably, the temperature of the material in the acylation reactor is 100-150°C, and the residence time of the material is 10 min-3 h; preferably, the residence time is 10 min-2.5 h. The conversion rate of phenolic hydroxyl groups in the reactants in this acetylation reaction is not less than 98%, and partial removal of acetic acid can occur during the acetylation process, but the amount of removed acetic acid is not more than 0.5 mol / mol of reactants.

[0074] Specifically, the temperature of the feed inlet of the devolatilization reactor 4 is 120-180℃; preferably, the temperature of the feed inlet of the devolatilization reactor 4 is 140-160℃. Specifically, the temperature of the liquid phase outlet of the devolatilization reactor 4 is equal to or greater than 220℃; preferably, the temperature of the liquid phase outlet of the devolatilization reactor 4 is equal to or greater than 235℃. During the residence of the material in the devolatilization reactor 4, the amount of acetic acid removed is not less than 0.45 mol / mol reactant, the acetic acid content at the liquid phase outlet of the devolatilization reactor 4 is not higher than 10 mol%, and the content of dimers and higher oligomers is not higher than 20 mol%. During the residence of the material in the devolatilization reactor 4, the average thickness is not higher than 10 mm, preferably, the average thickness is not higher than 2 mm. The residence time is not more than 600 seconds, preferably, the residence time is not more than 150 seconds.

[0075] Specifically, the temperature of the feed inlet of the devolatilization reactor 4 is 120-180℃; preferably, the temperature of the feed inlet of the devolatilization reactor 4 is 140-160℃. Specifically, the temperature of the liquid phase outlet of the devolatilization reactor 4 is equal to or greater than 220℃; preferably, the temperature of the liquid phase outlet of the devolatilization reactor 4 is equal to or greater than 235℃. During the residence of the material in the devolatilization reactor 4, the amount of acetic acid removed is not less than 0.45 mol / mol reactant, the acetic acid content at the liquid phase outlet of the devolatilization reactor 4 is not higher than 10 mol%, and the content of dimers and higher oligomers is not higher than 20 mol%. During the residence of the material in the devolatilization reactor 4, the average thickness is not higher than 10 mm, preferably, the average thickness is not higher than 2 mm. The residence time is not more than 600 seconds, preferably, the residence time is not more than 150 seconds.

[0076] From the above description, it can be seen that the present application achieves the following technical effects:

[0077] The present application utilizes the devolatilization reactor 4 to rapidly devolatilize the reactants, compared with the prior art, the present application has a shorter residence time in the homopolymerization temperature zone, effectively alleviating the occurrence of homopolymerization;

[0078] The present application utilizes the reheater 10 to reheat the acetic acid vapor generated in the acylation reactor and the devolatilization reactor 4, forms superheated acetic acid vapor, and then passes it into the devolatilization reactor 4 to continue devolatilization using the high temperature of the superheated acetic acid vapor, which has a larger gas phase acetic acid partial pressure, is conducive to inhibiting homopolymerization, and also achieves the effect of energy saving and consumption reduction;

[0079] The present application can be continuously fed and discharged, and is suitable for a process for semi-continuously or continuously preparing liquid crystal polymers;

[0080] The reaction process of the present application can all be carried out at atmospheric pressure, and the devolatilization reactor 4 can be made of inert inorganic non-metallic materials such as glass or ceramic, which has a lower construction cost compared with the strategy of using pressurization to retain acetic acid to avoid homopolymerization;

[0081] The temperature change of the present application is mainly in the devolatilization reactor 4, and the operating temperatures of the remaining reaction devices are basically constant, which has a lower difficulty in operation and design compared with the prior art.

[0082] In order to enable those skilled in the art to more clearly understand the technical solutions and technical effects of the present application, the following will be described in conjunction with specific embodiments. Specifically, the laboratory simulation device is used for demonstration.

[0083] The sources of the reaction materials of the following examples are as follows:

[0084] p-hydroxybenzoic acid (HBA) / 6-hydroxy-2-naphthoic acid (HNA) monomers: polymerization grade, 99.5% or more, Zhejiang Shengxiao Chemical Co., Ltd.;

[0085] Acetic anhydride: analytical pure (AR), 99%, National Pharmaceutical;

[0086] Acetic acid: AR, 99.5%, National Pharmaceutical;

[0087] Catalyst: zinc acetate, 1000 ppm.

[0088] Example 1

[0089] This example relates to the preparation of an acetylation reaction mixture.

[0090] This example was carried out at normal pressure, placing HBA 2 mol (276 g), HNA 0.5 mol (94 g), acetic anhydride 1.05 equivalents (2.625 mol, 268 g), and organic base catalyst 1000 ppm (relative to solid materials, 0.38 g) in a 1000 ml round-bottom flask, and connecting a condenser tube. After protection by nitrogen, stirring and heating to 140°C were carried out on a heating mantle. Due to the exothermic effect of the acetylation reaction, the materials began to boil and some acetic acid was evaporated. The reaction mixture was incubated at 140°C for 1 hour and was ready for use. The reaction was sampled and detected using nuclear magnetic resonance (NMR), specifically using deuterated methanol solvent, and the results are shown in Table 1 below.

[0091] Example 2

[0092] The difference between this example and Example 1 is that the reaction mixture was incubated at 120°C for 2 hours.

[0093] Example 3

[0094] The difference between this example and Example 1 is that the reaction mixture was incubated at 160°C for 30 minutes.

[0095] Table 1 Composition of the reaction mixture after acetylation reaction of Examples 1 to 3

[0096]

[0097]

[0098] In the table, ABA is 1-acetyloxy-4-benzoic acid, and ANA is 2-acetyloxy-6-naphthoic acid.

[0099] The contents of each HBA and HNA derivative monomer and oligomer in the table are obtained by integrating their characteristic NMR peak areas. Acetic anhydride content is estimated using the peak area of ​​methyl acetate due to hydrolysis during sample preparation. Acetic acid content is derived from the methanololysis of acetic anhydride, and its content is obtained by subtracting the acetic anhydride content from the acetic acid content obtained from the peak area.

[0100] Example 4

[0101] This embodiment relates to the preparation of devolatilized monomers.

[0102] like Figure 2 As shown, in this embodiment, the first column section 15 and the third column section 17 are each distillation columns filled with glass spring packing, each 300 mm in length. The second column section 16 is a spiked glass distillation column, 500 mm in length, with glass spring packing piled up to a height of about 2 cm at the top to ensure uniform fluid distribution. A straight connector 20 with a support nozzle connects the first column section 15 and the second column section 16. The acetylation reaction mixture is placed in a glass injection pump insulated with a heating jacket, and injected through the support nozzle using a first injection pump 22. A thermometer 18 and a reflux condenser 24 are located at the top of the first column section 15. The reflux ratio of the reaction is roughly controlled by adjusting the height of the insulation layer 19 at the top of the first column section 15 to ensure a small amount of reflux within the column. The bottom of the second column section 16 is connected to a flask for collection via a Y-shaped tee connector 21. The other outlet of the tee connector connects to the third column section 17. Acetic acid is pumped into the other end of the third column section 17 using the second injection pump 23, which provides acetic acid vapor. The second column section 16, the third column section 17, and the straight connector 20 are all heated using fiberglass heating tape. The temperature of the third column section 17 is measured at 260°C by a sensor at the bottom; the temperature of the second column section 16 is measured at 160°C by a sensor at the top and the heating at the devolatilization tower inlet; the first column section 15 is not actively heated but is insulated by wrapping it with insulation material. A thermometer 18 is installed at the top of the first column section 15 to detect the vapor temperature at the top. Except for a small amount of reflux, the remaining acetic acid is discharged from the top of the first column section 15 as saturated vapor and collected by a condenser. The monomer material flowing through the second column section 16 is collected and cooled in a product collection bottle at the bottom for later use, and its temperature is measured by a temperature sensor at the bottom of the second column section 16 for use in polymerization.

[0103] The experiment was performed using 200 g of the reaction mixture prepared in Example 1, with a pump rate of 1.5 ml / min for the material and 5.2 ml / min for the acetic acid. The sensor in the third column section 17 showed that the temperature of the acetic acid outflow was 259-260°C, the temperature at the inlet of the devolatilization column was 158-161°C, the temperature at the top of the column was maintained at 118-119°C, and the temperature at the bottom of the second column section 16 fluctuated between 235-242°C. The pumping of the material was completed in a total time of about 33 minutes. The material at the bottom of the column was sampled and subjected to NMR testing using deuterated methanol solvent, and the results are shown in Table 2 below.

[0104] Examples 5-8

[0105] Examples 5-8 differ from Example 4 in that the experiment was performed using the reaction mixture obtained in Example 2, and Examples 5-8 differ from each other in that different experimental conditions were used for devolatilization, as shown in Table 2 below.

[0106] Example 9

[0107] This example differs from Example 4 in that the experiment was performed using the reaction mixture obtained in Example 2.

[0108] Example 10

[0109] This example differs from Example 4 in that the experiment was performed using the reaction mixture obtained in Example 3.

[0110] Comparative Example 1

[0111] This comparative example relates to the preparation of devolatilized monomers, and specifically to the use of a kettle rectification method.

[0112] This comparative example simulates the working conditions of a kettle rectification process using a combination of glass instruments.

[0113] The 200 g of reaction mixture was placed in a 500 ml three-necked flask, a mechanical stirring device was installed in the middle neck, a rectification column with a height of 300 mm was installed in one side neck, the rectification column was filled with glass spring packing, nitrogen was introduced into the other side neck to maintain an inert atmosphere, and a thermometer was inserted for temperature control. A thermometer was installed at the top of the rectification column to monitor the temperature of the distillate. The three-necked flask was heated by an electric heating jacket, starting from 140°C, and the temperature of the electric heating jacket was increased by about 1°C per minute. The temperature of the distillate at the top of the column was monitored and controlled at about 118-119°C, and if the temperature was higher than 120°C, the heating power of the electric heating jacket was adjusted downward. After 110 min, the jacket temperature reached 240°C, and the reaction mixture in the three-necked flask was sampled and analyzed.

[0114] Comparative Example 2

[0115] This comparative example relates to the preparation of the devolatilized monomer, specifically using a simple distillation method.

[0116] This comparative example simulates the working condition of a simple distillation process using a glass apparatus combination.

[0117] The 200 g reaction mixture was placed in a 500 ml three-necked flask, a mechanical stirring device was installed in the middle neck, a common distillation head was installed in one side neck, a straight condenser tube was connected to recover the obtained acetic acid, the other side neck was connected to a nitrogen inlet to maintain an inert atmosphere, and a thermometer was inserted for temperature control. A thermometer was installed at the top of the distillation column to monitor the temperature of the distillate. The flask was heated by an electric heating jacket, starting from 140°C, and the temperature of the electric heating jacket was increased by about 1°C per minute. After 95 min, the jacket temperature reached 240°C, and the reaction mixture in the three-necked flask was sampled and analyzed.

[0118] Table 2 Experimental conditions and product composition of Examples 4 to 10 and Comparative Examples 1 and 2

[0119]

[0120]

[0121] Example 11

[0122] This example is the devolatilized monomer produced by the method of Example 4 that is subjected to melt polycondensation.

[0123] The devolatilized monomer produced in Example 4, 50 g, was reheated to 240°C to melt, and then heated to 340°C at a rate of 2°C / min, and stirring was maintained until a viscous, stringy melt was obtained. The melt was removed and analyzed for melting properties by differential scanning calorimetry (DSC), and the product properties are shown in Table 3 below.

[0124] Example 12

[0125] This example differs from Example 11 in that the devolatilized monomer used is the product of Example 5.

[0126] Example 13

[0127] This example differs from Example 11 in that the devolatilized monomer used is the product of Example 6.

[0128] Example 14

[0129] This example differs from Example 11 in that the devolatilized monomer used is the product of Example 7.

[0130] Example 15

[0131] This example differs from Example 11 in that the devolatilized monomer used is the product of Example 8.

[0132] Example 16

[0133] The difference between this example and Example 11 is that the devolatilized monomer used is the product of Example 9.

[0134] Example 17

[0135] The difference between this example and Example 11 is that the devolatilized monomer used is the product of Example 10.

[0136] Comparative Example 3

[0137] The difference between this comparative example and Example 11 is that the devolatilized monomer used is the product of Comparative Example 1.

[0138] Comparative Example 4

[0139] The difference between this comparative example and Example 11 is that the devolatilized monomer used is the product of Comparative Example 2.

[0140] Product properties of the products of Examples 11 to 17 and Comparative Examples 3 and 4

[0141]

[0142] From the above examples, it can be seen that the present application can effectively avoid the homopolymerization occurring in the devolatilization step and the adverse effects of the homopolymerization on the properties of the final polymerization product.

[0143] In the description of the present application, unless specifically defined and limited otherwise, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0144] In the present application, unless specifically defined and limited otherwise, "on" or "under" the first feature of the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature of the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" of the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0145] In the description of the present embodiments, the terms "upper", "lower", "left", "right", and the like, orientation or positional relationships are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only used to distinguish in the description, and have no special meaning.

[0146] The above embodiments are only used to illustrate the technical solutions of the present application and are not limited. The present application has been described in detail with reference to the preferred embodiments. Those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and all should be covered within the scope of the claims of the present application.

Claims

1. An apparatus for preparing a liquid crystal polymer, characterized in that, include: The reactor comprises a devolatilization reactor, a reheater, at least one polymerization reactor, and at least one acylation reactor; the liquid phase outlet of the acylation reactor is connected to the feed inlet of the devolatilization reactor, the gas phase outlet of the acylation reactor, the gas phase outlet of the devolatilization reactor, and the gas phase outlet of the polymerization reactor are all connected to the inlet of the reheater, the outlet of the reheater is connected to the gas phase inlet of the devolatilization reactor, and the liquid phase outlet of the devolatilization reactor is connected to the feed inlet of the polymerization reactor.

2. The apparatus for preparing liquid crystal polymers according to claim 1, characterized in that, The devolatilization reactor includes a reflux section, a rectification section, and a stripping section arranged sequentially within the shell; a feed inlet is provided between the rectification section and the stripping section, a gas phase outlet is provided at the upper part of the reflux section, and a gas phase inlet and a liquid phase outlet are provided at the lower part of the stripping section.

3. The apparatus for preparing liquid crystal polymers according to claim 2, characterized in that, The rectification section includes: a plate column or a packed column.

4. The apparatus for preparing liquid crystal polymers according to any one of claims 1 to 3, characterized in that, Also includes: A dissolving vessel, the outlet of which is connected to the feed inlet of the acylation reactor.

5. The apparatus for preparing liquid crystal polymers according to claim 4, characterized in that, The acylation reactor and / or the dissolution vessel are equipped with a stirrer.

6. The apparatus for preparing liquid crystal polymers according to any one of claims 1 to 3, characterized in that, Also includes: A condenser and a recovery tank; the inlet of the condenser is connected to the gas phase outlet of the devolatilization reactor and the inlet of the reheater, and the outlet of the condenser is connected to the recovery tank.

7. A method for preparing a liquid crystal polymer, characterized in that, The liquid crystal polymer is prepared using the preparation apparatus according to any one of claims 1 to 6, and the preparation method includes the following steps: Step 1) Weigh and mix the reactants, then add the acylation reagent and catalyst to dissolve them, and obtain the reaction solution; Step 2) The reaction solution undergoes acylation in an acylation reactor, followed by devolatilization in a devolatilization reactor, and then enters a polymerization reactor for polycondensation to obtain a polymer melt. Step 3) Cool the polymer melt and then crush and granulate it.

8. The method for preparing the liquid crystal polymer according to claim 7, characterized in that, The material temperature in the acylation reactor is between 100 and 160°C.

9. The method for preparing the liquid crystal polymer according to claim 7, characterized in that, The temperature at the feed inlet of the devolatilization reactor is 120–180°C.

10. The method for preparing the liquid crystal polymer according to claim 7, characterized in that, The feed inlet temperature of the polymerization reactor is greater than or equal to 220°C.

Images