CN-122011353-A - Imidazopyridine catalyst for liquid crystal polyarylester synthesis and application thereof

CN122011353ACN 122011353 ACN122011353 ACN 122011353ACN-122011353-A

Abstract

The invention relates to the field of polymer preparation, in particular to an imidazopyridine catalyst for liquid crystal polyarylester synthesis and application thereof, wherein the catalyst is an imidazopyridine 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, and the second set temperature is higher than the first set temperature. The imidazopyridine catalyst provided by the invention evaluates the thermal stability at high temperature by calculating the relative Gibbs free energy at different temperatures, so that the imidazopyridine catalyst shows excellent thermal stability in the melt polymerization of liquid crystal polyarylate (especially type II), can keep activity in the high-temperature melt polycondensation process of 200-350 ℃, thereby being beneficial to shortening the reaction time, effectively inhibiting the occurrence of side reaction, and finally enabling the prepared liquid crystal polyarylate product to have higher color value (L > 75) and improving the quality of the product.

Inventors

LIU HUI
ZHAO CHENXIA
ZHAO WANGTAO
SHI RUI
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. An imidazopyridine catalyst for synthesizing liquid crystal polyarylate, which is characterized in that, The catalyst is an imidazopyridine 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. The catalyst according to claim 1, it is characterized in that the method comprises the steps of, The imidazopyridine compound has a structure shown in a formula (I) or a formula (II): Formula (I); formula (II); Wherein R is selected from hydrogen, alkyl, alkoxy or halogen.
3. The catalyst according to claim 1 or 2, 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. A catalyst according to claim 3, it is characterized in that the method comprises the steps of, In step S2, the different temperatures include temperature points in a range of 0-1000K; In step S3, the first temperature is 298.15K and the second temperature is 300-1000K.
5. A method according to claim 1 to 4, wherein the catalyst is used for the synthesis of liquid crystalline polyarylates, The application comprises that the catalyst is used for melt polycondensation reaction of liquid crystal polyarylate, and the product with corresponding intrinsic viscosity is directly obtained.
6. A preparation method of liquid crystal polyarylate is characterized in that, Comprising acetylating an aromatic hydroxycarboxylic acid in the presence of the catalyst as claimed in any one of claims 1 to 4, and heating up to melt polycondensation after the completion of the acetylation, until the intrinsic viscosity liquid crystalline polyarylate is directly obtained after the completion of the reaction.
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. The method of claim 6 or 7, wherein, The temperature of the acetylation reaction in the polymerization step is 100-150 ℃; The temperature of the melt polycondensation reaction is 200-350 ℃.
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. The method of claim 6 or 7, wherein, The pressure of the melt polymerization reaction system is 0.01-100 kPa.

Description

Imidazopyridine catalyst for liquid crystal polyarylester synthesis and application thereof Technical Field The invention relates to the field of polymer preparation, in particular to an imidazopyridine catalyst for liquid crystal polyarylate synthesis and application thereof. Background In the process for preparing liquid crystal polyarylate by a melt polycondensation method, the selection of a catalyst is one of key factors influencing the performance of a polymer. The high-activity catalyst can effectively reduce the reaction activation energy and accelerate the polymerization rate, thereby reducing the residence time of the polymer in a high-temperature molten state, being beneficial to reducing the occurrence of side reactions such as thermal degradation and the like and having decisive influence on the molecular weight, the color and the processability of the final product. At present, the organic catalysts commonly used in the field comprise nitrogen-containing heterocyclic compounds such as N-methylimidazole and the like. However, in practical commercial production, such catalysts still face some challenges. For example, most of the catalysts contain only a single imidazole ring in the molecular structure, which results in single active site, and more importantly, some catalysts have insufficient thermal stability in the high-temperature polycondensation environment required by the liquid crystal polyarylate, which may decompose or volatilize, not only result in reduced catalytic efficiency at high temperature, but also make up for the problem of insufficient molecular weight through subsequent solid-phase polymerization procedures, increase the complexity and cost of the process, and may cause more side reactions due to the long residence time of the catalyst decomposition products or high temperature, which affects the color of the polymer. In order to screen for more efficient catalysts, researchers have tried various evaluation methods. Kinetic experiments are one of the traditional means to indirectly evaluate catalyst performance by monitoring the composition and concentration of gaseous products during the reaction. However, in the polycondensation reaction of liquid crystalline polyarylates, the gas phase composition is complicated, and the main by-products are not always direct indicators of catalytic activity, so that the accuracy of the method is limited, and the experiment itself is time-consuming and consumable. Computer-aided screening has shown potential as an alternative, for example, to predict the activity of small molecules by calculating their adsorption energy or reaction energy barrier at the catalyst surface. Such methods are effective for systems with relatively simple reactants and mechanisms, but their applicability is challenging in the synthesis of liquid crystalline polyarylates in such complex multi-step polymerization reactions. The reaction process involves a wide range of temperature changes, and involves small molecule cyclization, oligomer transformation and small molecule segment growth, which is not suitable for the basic reaction energy barrier of small molecule reaction at a single temperature or the adsorption energy at a single temperature to react the activity of the catalyst. Therefore, the development of a screening method which can give consideration to the calculation efficiency and effectively reflect the long-term heat stability of the catalyst in a complex polymerization system, particularly under the high-temperature condition, has important significance for the development of the catalyst for promoting the high-performance liquid crystal polyarylate. Disclosure of Invention The application provides an imidazopyridine catalyst for liquid crystal polyarylate synthesis and application thereof, and aims to overcome the defects that in the prior art, 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 order to achieve the aim of the invention, the invention is realized by the following technical scheme: in a first aspect, the present invention provides an imidazopyridine catalyst for liquid crystal polyarylate synthesis, The catalyst is an imidazopyridine 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. Preferably, the imidazopyridine compound has a structure as shown in formula (I) or formula (II): Formula (I); formula (II); Wherein R is selected from hydrogen, alkyl, alkoxy or halogen. Preferably, R may be hydrogen, methyl, ethyl, propyl, isopropyl, methoxy, ethoxy, fluoro, chloro, bromo, etc., including but not limited to the substituents listed, and the