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CN-122011354-A - Biimidazole catalyst for liquid crystal polyarylester synthesis and application thereof

CN122011354ACN 122011354 ACN122011354 ACN 122011354ACN-122011354-A

Abstract

The invention belongs to the field of synthesis of liquid crystal polyarylates, and particularly relates to a biimidazole catalyst for synthesis of liquid crystal polyarylates and application thereof, wherein the catalyst is a biimidazole compound, and the thermal stability of the catalyst is quantitatively evaluated, so that the Gibbs free energy at a second set temperature is lower than that at a first set temperature; wherein the second set temperature is higher than the first set temperature. The specific biimidazole catalyst obtained by screening in the invention has excellent thermal stability in the synthesis of the II-type liquid crystal polyarylate, can keep activity in the high-temperature melt polycondensation process of 200-350 ℃, thereby being beneficial to shortening the reaction time, effectively inhibiting side reactions caused by the decomposition of the catalyst, and finally enabling the prepared liquid crystal polyarylate product to have higher intrinsic viscosity and higher L value and improving the quality of the product.

Inventors

  • LIU HUI
  • ZHAO CHENXIA
  • SHI RUI
  • ZHAO WANGTAO
  • JIN JIYANG
  • ZHU WENXIANG

Assignees

  • 浙江海利得科技有限公司
  • 浙江海利得新材料股份有限公司
  • 海利得新材料研究(上海)有限公司

Dates

Publication Date
20260512
Application Date
20260317

Claims (10)

  1. 1. A biimidazole catalyst for synthesizing liquid crystal polyarylester is characterized in that, The catalyst is a biimidazole compound, and the thermal stability of the catalyst is quantitatively evaluated, so that the Gibbs free energy at a second set temperature is lower than the Gibbs free energy at a first set temperature, The second set temperature is higher than the first set temperature.
  2. 2. The catalyst according to claim 1, it is characterized in that the method comprises the steps of, The bisimidazole compound has a structure shown in a formula (I) or a formula (II) or a formula (III): Formula (I); formula (II); formula (III); Wherein R substituent is hydrogen, alkyl, alkoxy and halogen, R , is alkyl, phenyl, biphenyl, benzyl, pyridyl, pyridazinyl and pyrazinyl.
  3. 3. A screening method according to claim 1 or 2, wherein, The quantitative evaluation includes the steps of: S1, constructing a molecular model of a candidate catalyst, and performing geometric structure optimization and vibration frequency analysis to obtain an optimized molecular configuration; S2, calculating gibbs free energy of the candidate catalyst at different temperatures based on the optimized molecular configuration; And S3, calculating the relative Gibbs free energy change amount of the candidate catalyst at a second set temperature by taking the Gibbs free energy at the first set temperature as a reference, and evaluating the thermal stability of the candidate catalyst based on the relative Gibbs free energy change amount, wherein the numerical value of the relative Gibbs free energy change amount is more negative, and the thermal stability is higher.
  4. 4. The screening method according to claim 3, wherein, In step S2, the different temperatures include temperature points in a range of 0-1000K; in step S3, the first temperature is 298K a, and the second temperature is 300-1000 a K a.
  5. 5. The use of the biimidazole catalyst according to any one of claims 1-4 in the synthesis of liquid crystal polyarylate, it is characterized in that the method comprises the steps of, The application comprises that the biimidazole catalyst is used for melt polycondensation reaction of II-type liquid crystal polyarylate, and a product with corresponding intrinsic viscosity is directly obtained.
  6. 6. A preparation method of liquid crystal polyarylate is characterized in that, Comprising the step of acetylating an aromatic hydroxycarboxylic acid in the presence of the biimidazole-based catalyst as set forth in any one of claims 1 to 4, and performing melt polycondensation after the completion of the acetylating, wherein the liquid crystalline polyarylate having the intrinsic viscosity is directly obtained after the completion of the reacting.
  7. 7. The method of claim 6, wherein, The liquid crystal polyarylate is II-type liquid crystal polyarylate obtained by copolymerizing p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.
  8. 8. The method of claim 6 or 7, wherein, The temperature of the acetylation reaction in the polymerization step is 100-150 ℃ and the reaction time is 0.5-2 hours; The temperature of the melt polycondensation reaction is 200-350 ℃.
  9. 9. The method of claim 6 or 7, wherein, The addition amount of the catalyst is 10-1000 ppm of the total mass of the monomer reactants.
  10. 10. The method of claim 6 or 7, wherein, The pressure of the melt polymerization reaction system is 0.01-100 kPa.

Description

Biimidazole catalyst for liquid crystal polyarylester synthesis and application thereof Technical Field The invention belongs to the field of synthesis of liquid crystal polyarylates, and particularly relates to a biimidazole catalyst for synthesis of liquid crystal polyarylates and application thereof. Background Liquid crystalline polyarylates (Liquid Crystalline Polyarylates, LCP) are an intermediate state polymer between solid crystalline and liquid. The LCP has a low viscosity and is highly oriented when present as a liquid crystal phase, and its morphology is stable after cooling and solidification. The property enables the LCP material to have a series of excellent properties, such as high strength, high modulus, excellent molding processability, outstanding heat resistance, low water absorption, excellent flame retardance, extremely small linear expansion coefficient, excellent flame retardance, electrical insulation, chemical resistance, weather aging resistance, microwave permeability, low dielectric constant, dielectric loss factor and the like, and the LCP material has been widely applied to high and new technical industries of electronic appliances, automobile parts, aerospace, national defense and military industry and the like. The II-type liquid crystal polyarylester has the advantages of being wide in processing window, high in toughness and adjustable in dielectric property, and capable of showing unique advantages in high-end fields such as high-frequency circuit boards and 5G communication equipment by introducing part of flexible chain segments, and meanwhile, the processing performance is remarkably improved. The melt polycondensation is a main method for industrially synthesizing the II-type LCP, has the advantages of high polymerization degree, rapidness, simple equipment and the like, is widely used, and generally adopts p-acetoxybenzoic acid as a reaction monomer, and reacts between acetoxy and carboxyl groups of the p-acetoxybenzoic acid in a molten state to form a polymer, so that acetic acid byproducts are released. At present, the technical route is adopted by main manufacturers at home and abroad. The process has the remarkable advantages of no need of using solvents, reduction of environmental pollution and recovery cost, simple process flow, relatively low equipment investment, and high product purity, and can directly obtain a molten product for subsequent processing. However, the process has more problems that firstly, the reaction condition is harsh, the high-temperature reaction condition needs to be maintained for a long time, so that the energy consumption is high, secondly, the side reaction is difficult to control, the side reactions such as terminal group decomposition, molecular chain fracture, crosslinking and the like are easy to occur at high temperature, meanwhile, the viscosity of a reaction system in the polycondensation stage is rapidly increased along with the increase of the polymerization degree, and stirring difficulty and uneven mass transfer are extremely easy to cause, so that the molecular weight distribution of a polymer is influenced, and the material performance is further influenced. These defects cause large fluctuation of the performance among product batches, and become a main factor for restricting the development of industry. The oligomer can be obtained by melt polycondensation, and LCP with the required molecular weight is obtained by solid phase polymerization (CN 109535403A) under nitrogen or vacuum conditions, but the solid phase polymerization has longer time, larger energy consumption, uncontrollable molecular weight distribution and limited improvement effect. The industry is currently working to develop new catalyst systems to ameliorate the above problems. The catalyst system is usually an organic base catalyst except metal compounds, and according to the reaction mechanism, the alkalinity and nucleophilicity of the catalyst can effectively promote the reaction, especially an imidazole catalyst such as N-methylimidazole (CN 116199865A), but the boiling point of the N-methylimidazole is only 198 ℃, volatilization, bond breaking, alkyl substitution or dimerization and the like can occur under the high temperature condition of the II-type LCP synthesis, so that the catalytic failure is caused, the polymerization efficiency is seriously affected, the reaction time is long, the side reaction is increased, and the performance of the final polymer is affected. Disclosure of Invention The application provides a biimidazole catalyst for liquid crystal polyarylate synthesis and application thereof, and aims to overcome the defects that the catalyst for liquid crystal polyarylate synthesis has insufficient thermal stability at high temperature, so that the catalytic efficiency is reduced, side reactions are easy to initiate and the product quality is influenced in the prior art. In order to achieve the aim of the invention, the invention is r