Cleaning method of liquid crystal polyester reaction kettle

Abstract

The invention discloses a liquid crystal polyester reaction kettle cleaning method and belongs to the technical field of high polymer material production equipment cleaning. The method comprises the steps that a cleaning composition A is added into a reaction kettle where liquid crystal polyester is discharged, the cleaning composition A comprises alkali metal hydroxides and dihydric alcohol with the boiling point larger than 150 DEG C, the cleaning composition A is heated to the temperature 10-30 DEG C higher than the boiling point of the dihydric alcohol, backflow cleaning is conducted, and cleaning waste liquid is discharged and collected; adding a cleaning composition B into the reaction kettle, wherein the cleaning composition B is a byproduct acetic acid in the production process of the liquid crystal polyester; heating, refluxing and cleaning, and discharging pickling waste liquid after cleaning is finished; washing with water; carrying out reduced pressure distillation treatment on the discharged and collected cleaning waste liquid; and neutralizing the distilled kettle residual liquid until the pH value is 2-5, separating out a polymer monomer, and recovering the polymer monomer. The method has the advantages that energy consumption is reduced; the comprehensive cleaning cost is reduced; wastewater discharge is reduced; the cleaning agent has an excellent cleaning effect on adhered substances on the inner wall of a reaction kettle and a fractionating column; the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of cleaning technology for polymer material production equipment, and specifically relates to a cleaning method for a liquid crystal polyester reactor. Background Technology

[0002] Liquid crystal polyester (LCP) is widely used in electronics, aerospace, and precision instruments due to its excellent heat resistance, solvent resistance, and mechanical strength. LCP is typically produced using melt polycondensation, with raw materials including aromatic hydroxycarboxylic acids (such as p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid), aromatic diols (such as 4,4′-dihydroxybiphenyl), and aromatic dicarboxylic acids (such as terephthalic acid and isophthalic acid), which undergo polymerization at high temperatures (280–350°C).

[0003] A common technical challenge in the production of liquid crystal polyester is that after the polymerization reaction, some polymer adheres to the inner wall of the reactor, the surface of the agitator, the fractionation column, and other components, forming residues. Due to the excellent solvent resistance of liquid crystal polyester, these residues are difficult to remove with conventional solvents. If not thoroughly cleaned, these residues will carbonize and form impurities during the next polymerization reaction due to prolonged high temperatures, severely affecting the color and whiteness of the product, especially in applications requiring high quality, such as fibers and films.

[0004] To address the aforementioned problems, various cleaning methods have been proposed in the prior art. US5762718 discloses a process for reducing black spots in thermotropic liquid crystal polymers by continuously washing with triethylene glycol, ethylene glycol, and water. This patent employs a three-step cleaning process, sequentially cleaning the reactor with triethylene glycol (TEG), ethylene glycol (EG), and water. However, this process requires high temperatures (TEG cleaning temperature 330–355°C), resulting in high energy consumption, and TEG is expensive, leading to high cleaning costs. CN101812385A discloses a cleaning composition and a method for using it to clean liquid crystal polyester production equipment. The composition comprises (A) a diol, (B) an amine, and (C) a compound selected from cyclic esters, amides, and sulfoxides, wherein the content of component (B) is 5-40% by weight, and the content of component (C) is 5-30% by weight, both relative to the total weight of the cleaning composition. Cleaning can be performed at 190–240°C, but it still requires the use of various organic solvents and does not involve waste liquid recycling. CN103289835A discloses a cleaning composition and a method for cleaning a production apparatus using the same, comprising the following components: (a) an alcohol; (b) a highly polar compound selected from amides, sulfoxides, etc.; and (c) an alkali metal hydroxide. Component (a) accounts for 40-80% of the total volume of the cleaning composition, and component (b) accounts for 20-60% of the total volume. Specifically, the cleaning composition containing low-boiling-point alcohols (methanol, ethanol, etc.), highly polar compounds (DMSO, DMF, etc.), and alkali metal hydroxides can perform cleaning at temperatures below 100°C, and the whiteness value of the product is used as an evaluation index for cleaning effectiveness. However, the low-boiling-point alcohols used are highly volatile, pose significant safety hazards, and do not involve resource recycling.

[0005] The current situation is as follows: (1) The cleaning waste liquid is directly discharged, which causes environmental pollution and wastes resources; (2) The by-products in the production process are not considered for cleaning, which is not economically viable; (3) The cleaning steps are simple and have limited cleaning effect on complex structural parts such as distillation columns.

[0006] To address the aforementioned technical issues, exploring a cleaning method for liquid crystal polyester reactors that integrates efficient cleaning and resource recovery is of positive significance. This method can thoroughly remove residues from the inner wall of the reactor and the fractionation column, while also recovering cleaning solvents and polymer monomers to achieve resource recycling. Summary of the Invention

[0007] The objective of this invention is to provide a cleaning method for a liquid crystal polyester reactor. This method features low cleaning temperature, which saves energy; inexpensive solvents, which significantly reduce costs; recycling of cleaning waste liquid, which saves resources and avoids environmental pollution; and the ability to remove adhering substances from narrow parts such as fractionation columns, thus achieving a comprehensive cleaning effect.

[0008] The objective of this invention is to provide a cleaning method for a liquid crystal polyester reactor, comprising the following steps: A) Alkali-alcohol cleaning: Add cleaning composition A to the reaction vessel from which liquid crystal polyester has been discharged. Cleaning composition A contains an alkali metal hydroxide and a diol with a boiling point greater than 150°C. The mass concentration of the alkali metal hydroxide is 5-10%. Heat cleaning composition A to a temperature 10-30°C above the boiling point of the diol. Reflux cleaning is performed. The cleaning waste liquid is discharged and collected. B) Pickling: Add cleaning composition B to the reaction vessel after cleaning in step A). ​​The cleaning composition B is acetic acid, a by-product of the liquid crystal polyester production process, with a mass concentration ≥90%. Heat and reflux for cleaning. After cleaning, discharge the pickling waste liquid. C) Water washing: Add deionized water to the reaction vessel after acid washing in step B) and heat and reflux to wash; D) Diol recovery: The cleaning waste liquid discharged and collected in step A) is subjected to vacuum distillation. The distillation vacuum is -0.095MPa to -0.05MPa (gauge pressure), and the distillation temperature is 80 to 150℃. The recovered diols are then distilled. E) Monomer recovery: Neutralize the residue from distillation in step D) to pH 2-5, precipitate the polymer monomers, and recover them.

[0009] In a specific embodiment of the present invention, the mass concentration of the alkali metal hydroxide in step A) is 6-8%, the cleaning temperature is 15-25°C above the boiling point of the diol, and the reflux cleaning time is 3-5 hours.

[0010] In another specific embodiment of the present invention, the diol with a boiling point greater than 150°C is one or a mixture of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; and the alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide.

[0011] In another specific embodiment of the present invention, the mass concentration of the byproduct acetic acid in step B) is 95-98%, and the temperature of the heating and reflux washing is 105-115°C, and the time is 1.5-2.5 hours.

[0012] In another specific embodiment of the present invention, the water washing step described in step C) is repeated 1 to 3 times.

[0013] In another specific embodiment of the present invention, the vacuum degree of the vacuum distillation in step D) is -0.09MPa to -0.06MPa (gauge pressure), and the distillation temperature is 90 to 140°C.

[0014] In a more specific embodiment of the present invention, the neutralization in step E) is performed by neutralizing with hydrochloric acid to a pH value of 3-4.

[0015] In a further specific embodiment of the present invention, the polymer monomers described in step E) include one or more of p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 4,4′-dihydroxybiphenyl, terephthalic acid, and isophthalic acid.

[0016] In yet another specific embodiment of the present invention, the liquid crystal polyester reactor includes a reactor body and a stirrer, a distillation column, a condenser and other auxiliary equipment mounted on the reactor body.

[0017] In yet another specific embodiment of the present invention, the auxiliary equipment comprises an alkaline alcohol cleaning unit, an acid washing unit, a water washing unit, a diol recovery unit, and a monomer recovery unit connected to the reactor body.

[0018] One of the technical advantages of the present invention compared to existing technologies is that, by controlling the cleaning temperature at 10-30°C above the boiling point of the diol, energy consumption is significantly reduced. Secondly, by using inexpensive, commonly used diols such as ethylene glycol instead of expensive TEG, and by combining solvent recovery and monomer recovery for polymerization, the overall cleaning cost is greatly reduced. Thirdly, by utilizing the cleaning wastewater as a resource and reducing wastewater discharge, green environmental protection requirements are met. Fourthly, the synergistic cleaning process combining alkali-alcohol cleaning and acid washing effectively... The process decomposes and dissolves polymer residues on the inner wall of the reactor, while acid washing neutralizes residual alkali and dissolves specific types of oligomers. The synergistic effect of both methods results in excellent removal of adhering substances on the inner wall of the reactor and the fractionation column. The whiteness value of the liquid crystal polyester products produced after cleaning can reach over 88. Fifth, by neutralizing and recovering polymer monomers, waste is turned into treasure, significantly reducing production costs and embodying the spirit of a resource-saving circular economy. Sixth, using acetic acid, a byproduct of the liquid crystal polyester production process, as the acid washing medium achieves "waste treatment with waste," reducing the consumption of external reagents and waste emissions. Detailed Implementation

[0019] The present invention will be further illustrated below with specific embodiments, but the implementation of the present invention is not limited thereto. Specific conditions not specified in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0020] Distillation Parameter Design and Validation Instructions The vacuum distillation conditions used in step D) of this invention are designed based on the boiling point-pressure characteristics of different diols. The boiling point relationships of the main diols under different vacuum levels are as follows:

[0021] In step D) of this invention, the distillation temperature range of 80–150°C is matched with the vacuum range of -0.095 MPa to -0.05 MPa, which ensures effective distillation of the diol while avoiding monomer decomposition due to excessively high temperatures. Preferably, the conditions are a vacuum of -0.09 MPa to -0.06 MPa and a temperature of 90–140°C, which balances diol recovery rate and energy consumption.

[0022] Test methods 1. Evaluation of cleaning effect: After cleaning, observe the residue on the inner wall of the reactor and the surface of the fractionation column through the sight glass, and classify it according to the following standards: Advantages: The inner wall of the vessel and the surface of the fractionation column are smooth and free of visible residues; Good: The inner wall of the vessel is basically smooth, and there are trace amounts of residue on the surface of the fractionation column; In the middle section: there was a small amount of residue on the inner wall of the vessel and obvious residue on the surface of the fractionation column; Poor: There is a large amount of residue on the inner wall of the vessel, and the adhering substances on the surface of the fractionation column have not been removed.

[0023] 2. Product Whiteness Test: The test was conducted according to GB / T 2913~1982 "Test Method for Whiteness of Plastics". The cleaned liquid crystal polyester resin was injection molded into a 60mm×60mm×1mm square plate, and tested using a WSB-3 type whiteness meter (peak wavelength 457nm, meeting standard requirements) to obtain the whiteness value. A higher whiteness value indicates a lower impurity content in the product and a better cleaning effect.

[0024] 3. Diol recovery rate calculation: Recovery rate (%) = (mass of recovered diol / mass of initial diol) × 100%.

[0025] 4. Calculation of monomer recovery rate: Recovery rate (%) = (mass of recovered monomers / theoretically recoverable monomers) × 100%.

[0026] Example 1: A) Alkali-alcohol cleaning: In a 2000L stainless steel reactor equipped with a nitrogen inlet, stirrer, thermometer, reflux condenser, and fractionation column, after the production of liquid crystal polyester (obtained by melt polymerization of p-hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, terephthalic acid, and isophthalic acid) is completed, the molten polymer is discharged, the reactor is cooled to 150°C, and cleaning composition A is added: 1200L of ethylene glycol (boiling point 197°C) and 96kg of sodium hydroxide (mass concentration approximately 7.4%). Stirring is started, and the temperature is heated to 215°C (18°C above the boiling point of ethylene glycol). Cleaning is carried out under reflux for 4 hours (i.e., reflux cleaning for 4 hours). After cleaning, the cleaning waste liquid is discharged into a waste liquid storage tank. B) Pickling: Add cleaning composition B, consisting of 1000L of acetic acid (96% by mass), a byproduct of liquid crystal polyester production, to the reactor after cleaning in step A). ​​Heat to 110°C and reflux for 2 hours. After cleaning, discharge the pickling waste liquid. C) Water washing: Add 1200L of deionized water to the reaction vessel after acid washing in step B), heat to boiling, reflux for 1.5 hours, drain the wastewater, and repeat the water washing once. D) Diol recovery: The cleaning waste liquid extracted and collected in step A) was transferred into a distillation vessel and subjected to vacuum distillation at a vacuum degree of -0.085 MPa to -0.07 MPa and a temperature of 100 to 130 °C. The distillate was collected to obtain 1080 L of recovered ethylene glycol, with a recovery rate of 90.0%. E) Monomer recovery: The residue from distillation in step D) was cooled to 30°C, and industrial hydrochloric acid (31% by mass) was slowly added to neutralize it to pH 3.5. After stirring for 30 minutes, a large amount of white precipitate was observed to form. The precipitate was filtered, washed three times with deionized water, and dried under vacuum at 60°C to obtain 8.2 kg of recovered polymer monomers, i.e., a monomer mixture. Liquid chromatography analysis showed that the main components were p-hydroxybenzoic acid and 4,4′-dihydroxybiphenyl. The cleaning effect was rated as "excellent". The liquid crystal polyester produced using the cleaned reactor had a whiteness value of 89.2.

[0027] Example 2: A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, after completing the production of liquid crystal polyester, 1200L of cleaning composition A (1,4-butanediol, boiling point 235℃) and 84kg of sodium hydroxide (mass concentration approximately 6.5%) were added. The mixture was heated to 255℃ (20℃ above the boiling point) and refluxed for 3.5 hours. After the cleaning was completed, the waste liquid was collected. B) Pickling: Same as in Example 1; C) Washing with water: Same as in Example 1; D) Diol recovery: 1068 L of 1,4-butanediol was recovered by vacuum distillation under vacuum conditions of -0.09 MPa to -0.07 MPa and temperatures of 120–155 °C, with a recovery rate of 89.0%. E) Monomer recovery: Neutralize to pH 3.8, filter and dry, recover 7.9 kg of polymer monomers, and proceed as described in step E) of Example 1.

[0028] The cleaning effect was rated as "excellent", and the product whiteness value was 88.7.

[0029] Example 3: A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, add cleaning composition A: 1200L of ethylene glycol (boiling point 197°C), 60kg of sodium hydroxide (mass concentration of about 4.8%, slightly lower than the preferred range of the present invention) and 24kg of potassium hydroxide (mass concentration of total alkali metal hydroxides of about 6.5%), heat to 215°C, and reflux for cleaning for 4 hours; Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "excellent", the diol recovery rate was 89.5%, the polymer monomer recovery was 7.8 kg, and the product whiteness value was 88.9.

[0030] Example 4 (Verification of the lower limit of alkali concentration): A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, add cleaning composition A: 1200L of ethylene glycol and 60kg of sodium hydroxide (5.0% by mass), heat to 215°C, and reflux for 5 hours (extend the cleaning time to ensure effectiveness). Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "good", the diol recovery rate was 89.8%, the polymer monomer recovery was 7.2 kg, and the product whiteness value was 87.5.

[0031] Example 5 (Verification of the upper limit of alkali concentration): A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, add cleaning composition A: 1200L of ethylene glycol and 132kg of sodium hydroxide (mass concentration 10.0%), heat to 215°C, and reflux for cleaning for 3 hours; Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "excellent", the diol recovery rate was 88.5%, the polymer monomer recovery was 8.5 kg, and the product whiteness value was 89.0.

[0032] Example 6 (Different Diol Combinations): A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, add cleaning composition A: a mixture of 600L of ethylene glycol and 600L of 1,2-propanediol (boiling point 188°C), 96kg of sodium hydroxide (mass concentration approximately 7.4%), heat to 205°C (considering the boiling points of both alcohols), and reflux for 4 hours. Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "excellent", the recovery rate of mixed diols was 88.2%, the recovery rate of polymer monomers was 8.0 kg, and the whiteness value of the product was 88.3.

[0033] Example 7 (Verification under different vacuum conditions): A) Alkali-alcohol cleaning: Same as in Example 1; B) Pickling: Same as in Example 1; C) Washing with water: Same as in Example 1; D) Diol recovery: Comparative experiments were conducted using different vacuum conditions. Condition a (high vacuum): vacuum degree -0.095MPa to -0.09MPa, temperature 80~95℃, recovery rate 92.5%, but distillation time is prolonged; Condition b (medium vacuum): vacuum degree -0.08MPa to -0.07MPa, temperature 110~125℃, recovery rate 90.8%, and moderate distillation time; Condition c (low vacuum): vacuum level -0.06MPa to -0.05MPa, temperature 140~150℃, recovery rate 87.2%, short distillation time but high energy consumption. E) Monomer recovery: Same as in Example 1; Under the three conditions (i.e., conditions a, b, and c), there was no significant difference in the amount of polymer monomer recovered (8.0–8.3 kg). Considering both recovery rate and energy consumption, condition b (medium vacuum) was selected as the optimal operating range. The cleaning effect was "excellent" under all three conditions, and the whiteness values ​​of the products were 89.1, 89.0, and 88.9, respectively.

[0034] Comparative Example 1 (alkali and alcohol washing only, no acid washing): A) Alkali-alcohol cleaning: Same as in Example 1; B) Water washing: Direct water washing is performed, omitting the acid washing step; Steps C) to E) are the same as in Example 1; The cleaning effect was rated as "medium" (obvious residue was found in the fractionation column area), and the product whiteness value was 82.6.

[0035] Comparative Example 2 (Alkali concentration too low): A) Alkali-alcohol cleaning: Using the same reactor as in Example 1, add cleaning composition A: 1200L of ethylene glycol and 36kg of sodium hydroxide (mass concentration 3.0%, below the scope of this invention), heat to 215°C, and reflux for cleaning for 4 hours; Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "medium" (a small amount of residue remained on the inner wall of the vessel), and the product whiteness value was 80.3.

[0036] Comparative Example 3 (alkali concentration too high): A) Alkali-alcohol cleaning: Using the same reaction vessel as in Example 1, cleaning composition A was added: 1200L of ethylene glycol and 180kg of sodium hydroxide (mass concentration 13.0%, higher than the scope of this invention). The mixture was heated to 215°C and refluxed for 4 hours. During the cleaning process, the viscosity of the solution increased and a large amount of suspended matter was observed. Steps B)-E) are the same as in Example 1; The cleaning effect was rated as "good" (the cleaning effect was acceptable, but the waste liquid was difficult to treat). The diol recovery rate was only 75.2% (due to excessive impurities). The polymer monomer recovery was only 5.1 kg due to interference from suspended solids. The product whiteness value was 85.4.

[0037] Comparative Example 4 (US5762718 method): Referring to the method of Example 1 in US5762718: the reactor was cooled to 325°C, 10% TEG was added, and the reactor was refluxed at 345°C and 40 psi for 2 hours; after evacuation, 6% ethylene glycol was added, and the reactor was refluxed at 245°C and 40 psi for 45 minutes; after evacuation, the reactor was washed twice with water. The cleaning effect was rated as "excellent" and the product whiteness value was 88.5. However, solvent and monomer recovery were not carried out. Both TEG and EG were used only once, resulting in high cleaning costs.

[0038] Comparative Example 5 (Method CN103289835): Referring to Example 1 of CN103289835: The reactor was cooled to below 100°C, and 40L of methanol, 8kg of sodium hydroxide and 60L of DMSO were added. The reactor was then refluxed at 80°C for 3 hours. After emptying, the reactor was washed twice with water. The cleaning effect was rated as "good" (a small amount of residue was found in the fractionation column). The product whiteness value was 86.2. Methanol has a low boiling point, is easily volatile, and poses a significant safety hazard. DMSO is more expensive and has a strong odor.

[0039]

[0040] A comparison of the above embodiments and comparative examples shows that: (1) Examples 1 to 7 all achieved excellent cleaning results, with product whiteness values ​​≥87.5 and up to 89.2. At the same time, efficient recovery of diol (>88%) and effective recovery of monomer (7.2 to 8.5 kg) were achieved. Example 7 verified the effect of different vacuum conditions on the recovery rate, and the preferred vacuum range was -0.08 MPa to -0.07 MPa.

[0041] (2) Comparative Example 1 (without acid washing) shows that the acid washing step is crucial for thoroughly removing the adhering substances from parts such as the fractionation column, and the lack of acid washing will result in a significant decrease in the whiteness value of the product (82.6).

[0042] (3) Comparative Examples 2 and 3 show that the concentration of alkali metal hydroxide needs to be controlled within the range of 5 to 10%. If the concentration is too low, the cleaning effect is insufficient (whiteness 80.3), and if the concentration is too high, it will affect the subsequent recovery and may cause excessive corrosion (whiteness 85.4, low recovery rate).

[0043] (4) Although Comparative Example 4 (US5762718 method) has excellent cleaning effect (whiteness 88.5), it does not involve solvent recovery and monomer recovery, and the cost is high.

[0044] (5) Comparative Example 5 (CN103289835 method) showed moderate cleaning effect (whiteness 86.2), and there were safety hazards and cost issues related to solvent evaporation.

[0045] In summary, the method of the present invention achieves resource recovery of cleaning solvents and polymer monomers while ensuring excellent cleaning effect, resulting in significant economic and environmental benefits.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cleaning method for a liquid crystal polyester reactor, characterized in that: Includes the following steps: A) Alkali-alcohol cleaning: Add cleaning composition A to the reaction vessel from which liquid crystal polyester has been discharged. Cleaning composition A contains an alkali metal hydroxide and a diol with a boiling point greater than 150°C. The mass concentration of the alkali metal hydroxide is 5-10%. Heat cleaning composition A to a temperature 10-30°C above the boiling point of the diol. Reflux cleaning is performed. The cleaning waste liquid is discharged and collected. B) Pickling: Add cleaning composition B to the reaction vessel after cleaning in step A). ​​The cleaning composition B is acetic acid, a by-product of the liquid crystal polyester production process, with a mass concentration ≥90%. Heat and reflux for cleaning. After cleaning, discharge the pickling waste liquid. C) Water washing: Add deionized water to the reaction vessel after acid washing in step B) and heat and reflux to wash; D) Diol recovery: The cleaning waste liquid discharged and collected in step A) is subjected to vacuum distillation. The distillation vacuum is -0.095MPa to -0.05MPa and the distillation temperature is 80 to 150℃ to recover the diol. E) Monomer recovery: Neutralize the residue from distillation in step D) to pH 2-5, precipitate the polymer monomers, and recover them.

2. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: The mass concentration of the alkali metal hydroxide in step A) is 6-8%, the cleaning temperature is 15-25°C above the boiling point of the diol, and the reflux cleaning time is 3-5 hours.

3. A cleaning method for a liquid crystal polyester reactor according to claim 1 or 2, characterized in that: The diol with a boiling point greater than 150°C is one or a mixture of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; the alkali metal hydroxide is sodium hydroxide and / or potassium hydroxide.

4. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: In step B), the mass concentration of the byproduct acetic acid is 95-98%, and the temperature of the heating and reflux washing is 105-115°C, and the time is 1.5-2.5 hours.

5. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: The water washing step described in step C) is repeated 1 to 3 times.

6. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: The vacuum degree of the reduced pressure distillation described in step D) is -0.09MPa to -0.06MPa, and the distillation temperature is 90 to 140℃.

7. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: The neutralization described in step E) involves neutralizing with hydrochloric acid to a pH of 3-4.

8. The cleaning method for a liquid crystal polyester reactor according to claim 1, characterized in that: The polymer monomers described in step E) include one or more of p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 4,4′-dihydroxybiphenyl, terephthalic acid, and isophthalic acid.

9. A cleaning method for a liquid crystal polyester reactor according to any one of claims 1 to 8, characterized in that: The liquid crystal polyester reactor includes a reactor body and a stirrer, a distillation column, a condenser, and other auxiliary equipment mounted on the reactor body.

10. A cleaning method for a liquid crystal polyester reactor according to claim 9, characterized in that: The auxiliary equipment includes an alkali-alcohol cleaning unit, an acid washing unit, a water washing unit, a diol recovery unit, and a monomer recovery unit connected to the reactor body.

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