A method for preparing an active ester curing agent

Abstract

This invention relates to the field of chemical synthesis technology and discloses a method for preparing an active ester curing agent. The method includes: preparing a fluorinated bicyclic carbonate monomer by cyclization addition of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether; continuously acylating the monomer with 2,6-naphthalenedicarboxyl chloride in a microchannel reactor to obtain a fluorinated cyclic carbonate-terminated diester intermediate; selectively ending some phenolic hydroxyl groups of spirobifluorene with pentafluorobenzoyl chloride to obtain a fluorinated spirocyclic diphenol intermediate; and co-condensing the two intermediates with isophthalic acid, followed by purification to obtain the active ester curing agent.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and more specifically, to a method for preparing an active ester curing agent. Background Technology

[0002] Spirodifluorene-based active ester curing agents, due to their rigid spirocyclic structure, can effectively suppress dipole polarization loss and have broad application prospects in the field of high-frequency electronic packaging substrates. To meet the low-temperature packaging requirements of heat-sensitive components, existing technologies introduce cyclic carbonate end-capping groups into the active ester molecular chain. These groups utilize the heat released by their ring-opening reaction with amines to achieve a self-catalytic effect, reducing the curing temperature from 200-220℃ to 150-165℃.

[0003] However, the aforementioned existing technologies have the following drawbacks: First, the β-hydroxy groups and NH groups in urethane esters generated after ring opening of cyclic carbonates are strongly polar hydrophilic groups, becoming hydrogen bond anchoring sites for water molecules, increasing the water absorption rate of the cured product and drastically worsening dielectric loss under high temperature and humidity conditions. Second, the local temperature gradient of the intermittent batch acylation reaction can reach 15 to 25°C during scale-up production, exceeding the thermal stability threshold of cyclic carbonates, resulting in large fluctuations in the retention rate of cyclic carbonate groups and poor product consistency. Third, when directly introducing fluorinated hydrophobic monomers for co-condensation, the solubility parameters of the fluorinated segments and spirodifluorene segments differ greatly, leading to microphase separation in the later stages of polycondensation and decreased product uniformity. These drawbacks make it difficult for existing reactive ester curing agents to simultaneously meet the comprehensive requirements of low-temperature curing, low hygroscopicity, and product consistency. Summary of the Invention

[0004] This invention provides a method for preparing an active ester curing agent, which solves the technical problems of insufficient heat resistance, low curing activity, and poor batch stability of active ester curing agents due to structural design limitations in related technologies.

[0005] This invention discloses a method for preparing an active ester curing agent, comprising the following steps: 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether and A cyclization addition reaction was carried out under the action of a catalyst to obtain a fluorinated bicyclic carbonate monomer. The fluorinated bicyclic carbonate monomer, 2,6-naphthalenedicarboxylate chloride, and organic base were each prepared into solutions and then simultaneously injected into a microchannel reactor. to A continuous acylation reaction was carried out at ℃, and the fluorinated cyclic carbonate-terminated diester intermediate was obtained after purification. Spirobifluorene and pentafluorobenzoyl chloride were reacted in the presence of an organic base. to Partial phenolic hydroxyl group esterification and capping were performed at ℃ to obtain a fluorinated spirocyclic diol intermediate; The fluorinated spirocyclic biphenol intermediate, the fluorinated cyclic carbonate-terminated diester intermediate, and isophthalic acid were reacted in the presence of an transesterification catalyst. to The active ester curing agent is obtained by co-condensation reaction at ℃ and then purified.

[0006] Furthermore, in the cyclization addition reaction, Parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether dissolved in to In the anhydrous N,N-dimethylacetamide, the catalyst is tetrabutylammonium bromide, and the amount used is... to Parts by weight Pressure is to MPa, reaction temperature is to ℃, reaction time is to h; after the reaction was completed, anhydrous N,N-dimethylacetamide was removed by vacuum distillation, and the fluorinated bicyclic carbonate monomer was obtained by recrystallization with ethyl acetate.

[0007] Further, the fluorinated bicyclic carbonate monomer, 2,6-naphthalenedicarboxylate chloride, and organic base are dissolved in anhydrous tetrahydrofuran to prepare solutions; the inner diameter of the microchannel reactor is... to mm, the residence time of the continuous acylation reaction is to s; The molar ratio of the fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride is to The organic base used in the continuous acylation reaction is N,N-diisopropylethylamine, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride is [missing information]. to .

[0008] Furthermore, the microchannel reactor inlet adopts a T-type or Y-type mixing structure. After the fluorinated bicyclic carbonate monomer solution and the 2,6-naphthalenedicarboxylate chloride solution converge at the first mixing point, the mixture is then disposed of downstream of the first mixing point. to At mm, the solution of N,N-diisopropylethylamine merges with the solution at the second mixing point, achieving segmented mixing and feeding.

[0009] Furthermore, the partial phenolic hydroxyl esterification capping is carried out in anhydrous dichloromethane; the molar ratio of pentafluorobenzoyl chloride to spirobifluorene in the phenolic hydroxyl groups is [missing information]. to The organic base used in the esterification capping is triethylamine, and the molar ratio of triethylamine to pentafluorobenzoyl chloride is [value missing]. to The triethylamine was added at a time when... to h, the heat preservation reaction time is to h.

[0010] Furthermore, in the copolymerization reaction, the amount of the fluorinated end-capped spirocyclic diol intermediate is: to The amount of the fluorinated cyclic carbonate-terminated diester intermediate is in parts by weight. to The amount of isophthalic acid used is (parts by weight). to Parts by weight; the transesterification catalyst is tetrabutyl titanate, and the amount used is... to Parts by weight; the reaction solvent is mesitylene, and the amount used is [amount] of the total mass of the solid materials. to The time for the co-condensation reaction is [times missing]. to h.

[0011] Furthermore, the cocondensation reaction is carried out using a programmed temperature ramp: first at... to reaction at ℃ to h completes the pre-condensation polymerization, then heats up to to ℃ reaction to h completes deep polycondensation.

[0012] Further, the purification includes washing the effluent from the continuous acylation reaction with deionized water. to The pH of the secondary aqueous phase is to The organic phase is separated, and after dehydration with anhydrous magnesium sulfate, it is subjected to a vacuum. to MPa, temperature to The solvent was removed at ℃ to obtain the fluorinated cyclic carbonate-terminated diester intermediate.

[0013] Further, the refining process includes: cooling the cocondensation product to... to ℃, diluted with mesitylene to a solid content to Parts by weight Parts by weight, through an aperture of to Filtration with a μm filter membrane, in to ℃, vacuum degree to Degassing at MPa to h; the resulting active ester curing agent Viscosity at ℃ to mPa·s, weight-average molecular weight is to g / mol.

[0014] This invention discloses an active ester curing agent, which is prepared by the above-described preparation method.

[0015] The beneficial effects of this invention are as follows: This invention uses 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether as a raw material to prepare fluorinated bicyclic carbonate monomers. During the curing process, the β-hydroxyl group generated by the ring-opening of the carbonate is directly located at the ortho position of the hexafluoroisopropyl group. The strong electron-withdrawing effect of the hexafluoroisopropyl group weakens the hydrogen bond donor ability of the β-hydroxyl group. The perfluorocarbon chain forms a hydrophobic shield for the hydroxyl group in space. This solves the technical problem that the strong hydrophilicity of the ring-opening product of cyclic carbonate leads to an increase in the moisture absorption rate of the cured product. It achieves the technical effect of inhibiting the moisture absorption of the cured product while retaining the self-catalytic cooling and curing function of cyclic carbonate.

[0016] This invention employs a microchannel reactor for continuous acylation, whose extremely high specific surface area heat transfer characteristics allow the temperature gradient in the reaction zone to be controlled within ±1℃. This solves the technical problem of local overheating leading to the decomposition of cyclic carbonate groups and poor product consistency during the scale-up of batch-type acylation reactions, and achieves the technical effect of improving the consistency of cyclic carbonate group retention rates between batches.

[0017] This invention selectively caps some of the phenolic hydroxyl groups of spirobifluorene with pentafluorobenzoyl chloride, allowing the fluorinated components to disperse in the polymer backbone in the form of chemical bonds. This solves the technical problem of microphase separation caused by differences in solubility parameters when fluorinated monomers are directly polycondensed as free comonomers, and achieves the technical effect of improving the uniformity of polycondensation products. At the same time, the pentafluorobenzoate capping group and hexafluoroisopropyl group together form a multi-level fluorinated hydrophobic structure, which further inhibits the adsorption of moisture by the cured product and improves the dielectric loss stability of the cured product under high temperature and high humidity conditions. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the preparation process of the active ester curing agent provided in the embodiments of the present invention; Figure 2This is a schematic diagram comparing the retention rates of cyclic carbonate groups in various embodiments and comparative examples provided in this invention. Figure 3 This is a schematic diagram comparing the batch consistency of microchannel process and batch process provided in the embodiments of the present invention; Figure 4 This is a schematic diagram showing a comprehensive comparison of the water absorption rate of the cured material and the increase in dielectric loss under high temperature and high humidity, provided in an embodiment of the present invention. Figure 5 This is a schematic diagram comparing the dielectric loss (tanδ) of various samples at room temperature and humidity with that at high temperature and humidity, provided in the embodiments of the present invention; Figure 6 This is a schematic diagram of the FTIR spectrum of the fluorinated bicyclic carbonate monomer (intermediate A) provided in the embodiments of the present invention; Figure 7 This is a schematic diagram of the SEM morphology of the active ester curing agent product (sample 2) provided in the embodiments of the present invention; Figure 8 This is a schematic diagram comparing the DSC curing curves of the cured products of Example 2 and the comparative example provided in this invention. Detailed Implementation

[0019] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0020] At least one embodiment of the present invention discloses a method for preparing an active ester curing agent, comprising: Step 1: Preparation of fluorinated bicyclic carbonate monomers 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether (epoxy value 0.53 to 0.58 eq / 100g, number average molecular weight 470 to 490 g / mol, viscosity at 25°C 1200 to 1800 mPa·s) were dissolved in 200 to 300 parts by weight of anhydrous N,N-dimethylacetamide, and the solution was introduced into the reaction system. The gas pressure was increased to 2 to 5 MPa, and 3 to 6 parts by weight of tetrabutylammonium bromide were added. The reaction was carried out at 100 to 130 °C for 8 to 14 h to achieve cyclization addition. After the reaction was completed, anhydrous N,N-dimethylacetamide was removed by vacuum distillation, and then purified by recrystallization with ethyl acetate to obtain a fluorinated bicyclic carbonate monomer with hexafluoroisopropyl bridging.

[0021] Furthermore, the above-mentioned vacuum distillation conditions are a vacuum of -0.085 to -0.095 MPa and a temperature of 80 to 100 °C. Recrystallization is performed using ethyl acetate as the solvent; after hot dissolution, the temperature is lowered to 0 to 5 °C at a rate of 0.5 to 1.0 °C / min to induce crystallization. The crystals are collected by filtration and dried in an oven at 40 to 50 °C to constant weight. A purging process is then initiated. The preferred pressure is 3 to 4 MPa, which ensures... The high solubility of tetrabutylammonium bromide in anhydrous N,N-dimethylacetamide allows for a high conversion rate in the cyclization addition reaction. The preferred reaction temperature is 110 to 120°C, within which the tetrabutylammonium bromide exhibits good hydration of the epoxy group and... The cyclization addition reaction exhibits high catalytic activity while avoiding side reactions caused by excessively high temperatures.

[0022] Furthermore, the conversion rate of the cyclization addition reaction was determined by proton nuclear magnetic resonance spectroscopy (NMR 1H). The determination was performed using the integral area attenuation ratio of the epoxy group characteristic peak (chemical shift 2.6 to 3.1 ppm), calculated as follows: ,in For conversion rate, This represents the integrated area of ​​the characteristic peak of the epoxy group before the reaction. This represents the integral area of ​​the characteristic peak of the epoxy group after the reaction.

[0023] Furthermore, the cyclization addition reaction in step 1 is carried out in a closed, pressure-resistant reactor. Before introducing nitrogen, the reaction system must be purged with nitrogen three times to remove moisture and air from the system. The feed rate is controlled to allow the pressure inside the vessel to rise steadily to the target pressure within 30 to 60 minutes. During the pressurization process, stirring is carried out continuously at a speed of 200 to 300 rpm.

[0024] Furthermore, after removing anhydrous N,N-dimethylacetamide by vacuum distillation in step 1, residual anhydrous N,N-dimethylacetamide may remain in the crude product in trace amounts. After recrystallization, the resulting crystals must be washed 2 to 3 times with cold ethyl acetate (0 to 5°C), each time using 1 to 2 times the mass of the crystals, to thoroughly remove residual anhydrous N,N-dimethylacetamide and tetrabutylammonium bromide. After washing, the crystals are dried in an oven at 40 to 50°C to constant weight.

[0025] Furthermore, ethyl acetate in step 1 is a flammable organic solvent, and the recrystallization operation must be carried out in a fume hood, away from open flames and heat sources. Anhydrous N,N-dimethylacetamide recovered by vacuum distillation is a toxic and hazardous organic waste liquid and must be collected in a dedicated waste liquid container and disposed of by a professional waste liquid treatment facility; it must not be dumped into sewers. The ethyl acetate-containing waste liquid generated from recrystallization washing must also be collected separately and disposed of in a unified manner.

[0026] It should be noted that the role of the hexafluoroisopropyl bridging structure in the aforementioned 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether is as follows: after the cyclization addition, the five-membered carbonate ring in the resulting fluorinated bicyclic carbonate monomer is ortho-positioned with the hexafluoroisopropyl group. During subsequent curing, the β-hydroxyl group generated from the carbonate ring opening is directly adjacent to the hexafluoroisopropyl group. The strong electron-withdrawing effect of the perfluoroalkyl group weakens the hydrogen bond donor ability of the β-hydroxyl group, while the perfluorocarbon chain forms a hydrophobic shield for the hydroxyl group in space, thus suppressing the hydrophilicity of the ring-opening product at the molecular level.

[0027] Step 2: Preparation of material solution The fluorinated bicyclic carbonate monomer obtained in step 1 is dissolved in anhydrous tetrahydrofuran to prepare material A, a solution with a concentration of 30 to 40 parts by weight per 100 parts by weight. 2,6-Naphthalenedicarboxylate chloride (acyl chloride content ≥99.0%, molecular weight 253.08 g / mol) is dissolved in anhydrous tetrahydrofuran to prepare material B, a solution with a concentration of 20 to 30 parts by weight per 100 parts by weight. N,N-Diisopropylethylamine is dissolved in anhydrous tetrahydrofuran to prepare material C, a solution with a concentration of 10 to 15 parts by weight per 100 parts by weight.

[0028] Furthermore, the concentration of material A is preferably 35 parts by weight / 100 parts by weight, the concentration of material B is preferably 25 parts by weight / 100 parts by weight, and the concentration of material C is preferably 12 parts by weight / 100 parts by weight. This concentration range ensures that each material has suitable flowability and mixing efficiency in the microchannel reactor, while avoiding channel blockage due to excessively high concentration or insufficient production efficiency due to excessively low concentration.

[0029] Furthermore, the preparation of materials A, B, and C was carried out at 20 to 25°C, with a stirring speed of 200 to 400 rpm and a stirring time of 20 to 40 minutes, until the solids were completely dissolved and the solution was clear and transparent. Before use, each prepared solution should be stored in a sealed container away from light, at a temperature not exceeding 25°C, and for a period not exceeding 24 hours.

[0030] Furthermore, the preparation of materials A, B, and C is carried out under dry nitrogen protection. The moisture content of the anhydrous tetrahydrofuran used must be less than 50 ppm. The preparation containers must be purged with nitrogen before use to prevent the hydrolysis of 2,6-naphthalenedicarboxyl chloride and the hygroscopic absorption of fluorinated bicyclic carbonate monomers.

[0031] Furthermore, anhydrous tetrahydrofuran is a flammable, low-boiling-point organic solvent with some neurotoxicity. When preparing solutions, it must be done in a fume hood, away from open flames and static electricity. Operators must wear organic solvent-resistant gloves and safety goggles. 2,6-Naphthalenedicarboxylate reacts violently with water, releasing hydrogen chloride gas, which is highly corrosive. Opening and weighing operations must be performed in a fume hood under dry nitrogen protection. Operators must wear acid and alkali-resistant gloves and masks.

[0032] Step 3: Microchannel continuous acylation reaction Materials A, B, and C were simultaneously injected into a microchannel reactor with an inner diameter of 1 to 3 mm using precision metering pumps. The molar ratio of the fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride was 2.1 to 2.4:1, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride was 2.2 to 2.8:1. The reaction temperature was controlled at -5 to 8°C, and the residence time was 40 to 150 s to complete the acylation reaction. The effluent continuously flowed into a collection container to obtain a fluorinated cyclic carbonate-terminated naphthalenedicarboxylate reaction solution.

[0033] Furthermore, the inner diameter of the microchannel reactor is preferably 1.5 to 2.0 mm, and the residence time is preferably 60 to 100 s. The microchannel reactor utilizes its extremely high specific surface area for heat transfer, controlling the temperature gradient in the reaction zone within ±1℃. Compared to the localized temperature gradient of 15 to 25℃ in batch acylation reactions, the precise temperature control of the microchannel reactor prevents the thermal decomposition of cyclic carbonate groups due to localized overheating, thus maintaining a stable high retention rate of cyclic carbonate groups.

[0034] Furthermore, the retention rate of cyclic carbonate groups was determined by Fourier transform infrared spectroscopy (FTIR) from 1800 to 1820. The ratio of the integrated area of ​​the characteristic absorption peak of the carbonyl group of the cyclic carbonate to the integrated area of ​​the internal standard peak is calculated using the following formula: ,in The retention rate of cyclic carbonate groups. The integral area represents the characteristic peak of the carbonyl group in cyclic carbonates. The integral area of ​​the inner standard peak.

[0035] It should be noted that the molar ratio of the fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride is preferably 2.2 to 2.3:1. The excess fluorinated bicyclic carbonate monomer ensures that both acyl chloride groups at both ends of the 2,6-naphthalenedicarboxylate chloride are capped by the fluorinated bicyclic carbonate monomer, forming a diester structure capped with bicyclic carbonates. This avoids uncontrollable crosslinking reactions caused by residual acyl chloride groups during subsequent polycondensation.

[0036] Furthermore, the microchannel reactor inlet adopts a T-type or Y-type mixing structure. After material A and material B merge at the first mixing point, they merge with material C at the second mixing point 5 to 15 mm downstream of the first mixing point, achieving segmented mixing. This segmented feeding method allows the initial contact between 2,6-naphthalenedicarboxylate chloride and the alcohol hydroxyl groups in the fluorinated bicyclic carbonate monomer to be completed in an extremely short channel for premixing. Subsequently, the addition of N,N-diisopropylethylamine promptly neutralizes the generated hydrogen chloride, avoiding the catalytic hydrolysis of the cyclic carbonate groups by the acidic environment.

[0037] Furthermore, when materials A, B, and C are injected into the microchannel reactor via precision metering pumps, the flow rates of each material are monitored in real time by flow meters, and flow fluctuations are controlled within ±2% of the set value to ensure a stable molar ratio of each material at the mixing point. The temperature of the microchannel reactor is controlled by an external circulating cooling bath, with the cooling medium being an aqueous solution of ethylene glycol. The cooling bath temperature is set 3 to 5°C lower than the target reaction temperature.

[0038] Furthermore, the microchannel reactor and all material delivery pipelines must be purged with dry nitrogen gas for at least 10 minutes before the reaction begins to remove residual moisture and air from the pipelines and prevent hydrolysis of 2,6-naphthalenedicarboxylate before it enters the reaction channel. The collection container is pre-filled with nitrogen for protection, and the outlet material is continuously collected under nitrogen cover.

[0039] Furthermore, the hydrogen chloride gas generated during the acylation reaction is neutralized by N,N-diisopropylethylamine to form an amine salt. If a small amount of unneutralized hydrogen chloride escapes from the outlet of the microchannel reactor, it must be absorbed by an alkaline solution (5 to 10% sodium hydroxide aqueous solution) before being discharged. The operating area must be well ventilated.

[0040] Step 4: Subsequent purification of the reaction solution The fluorinated cyclic carbonate-terminated naphthalene dicarboxylate reaction solution obtained in step 3 was subjected to online liquid-liquid washing to remove amine salts. The washing solvent was deionized water, and the washing was repeated 3 to 5 times until the pH of the aqueous phase reached 6 to 7. The organic phase was then separated. After dehydration by passing the organic phase through an anhydrous magnesium sulfate packed column, it was fed into a thin-film evaporator to continuously remove anhydrous tetrahydrofuran at a vacuum of -0.085 to -0.095 MPa and a temperature of 45 to 55 °C, yielding the fluorinated cyclic carbonate-terminated diester intermediate.

[0041] Furthermore, the preferred temperature for the thin-film evaporator is 48 to 52°C. This temperature range effectively removes anhydrous tetrahydrofuran (boiling point 66°C) while remaining well below the thermal decomposition temperature of cyclic carbonate groups, thus avoiding the loss of active groups during evaporation.

[0042] Furthermore, in the liquid-liquid washing and separation operation, the amount of deionized water used in each wash is 0.5 to 1.0 times the volume of the organic phase, the washing temperature is 20 to 30°C, and the settling time for each wash is no less than 15 minutes. The pH of the aqueous phase is measured using a precision pH meter, and the washing is considered complete when the pH of the aqueous phase is within the range of 6 to 7 after two consecutive washes.

[0043] Furthermore, the amine-containing brine phase generated from the liquid-liquid washing in step 4 must be collected and treated uniformly, and must not be discharged directly. The aqueous phase containing N,N-diisopropylethylamine hydrochloride is alkalized (adjusted to pH 10 to 12), and then N,N-diisopropylethylamine is recovered by extraction with ethyl acetate. The remaining aqueous phase is neutralized to pH 6 to 8 and then disposed of according to the waste liquid procedure.

[0044] Furthermore, the anhydrous tetrahydrofuran vapor removed by the thin-film evaporator must be recovered by a condenser at a condensation temperature of -10 to 0°C. The recovered anhydrous tetrahydrofuran, after drying, can be recycled for the preparation of the material solution in step 2, thereby reducing the consumption of organic solvents. Any small amount of tetrahydrofuran vapor that cannot be recovered by condensation must be treated by an activated carbon adsorption device before being discharged. Waste anhydrous magnesium sulfate desiccant, after adsorbing organic matter, must be collected as solid waste and disposed of by a professional organization.

[0045] Step 5: Preparation of fluorine-containing end-capped spirocyclic diol intermediate 60 to 90 parts by weight of spirobifluorene (hydroxyl value 280 to 310 mg KOH / g, purity ≥98.5%) and 8 to 18 parts by weight of pentafluorobenzoyl chloride (purity ≥99.0%, molecular weight 230.56 g / mol) were added to anhydrous dichloromethane, wherein the amount of anhydrous dichloromethane was 3 to 6 times the mass of spirobifluorene. The mixture was stirred until the solid was completely dissolved. After the system temperature was lowered to 0 to 10 °C, triethylamine was added dropwise through a constant pressure dropping funnel. The molar ratio of triethylamine to pentafluorobenzoyl chloride was 1.0 to 1.5:1. The dropping time was controlled at 0.5 to 1 h, and the reaction was maintained at this temperature for 1 to 2 h to allow some of the phenolic hydroxyl groups to be capped with pentafluorobenzoic acid esters. After the reaction was completed, the triethylamine hydrochloride precipitate was removed by filtration. The filtrate was then subjected to vacuum distillation at 40 to 50 °C and a vacuum degree of -0.085 to -0.095 MPa to remove anhydrous dichloromethane, yielding a fluorinated spirocyclic diol intermediate.

[0046] Furthermore, the acylation reaction in step 5 is carried out under nitrogen protection. Nitrogen is continuously introduced during the solid dissolution and cooling process at a flow rate of 0.05 to 0.10 L / min to prevent the pentafluorobenzoyl chloride from absorbing moisture and hydrolyzing, and to prevent moisture in the system from affecting the acylation selectivity. Triethylamine must be dried to a moisture content below 100 ppm before use.

[0047] Furthermore, anhydrous dichloromethane is volatile and neurotoxic, and pentafluorobenzoyl chloride reacts with water to release hydrogen fluoride and hydrogen chloride, exhibiting strong corrosiveness and toxicity. All operations in step 5 must be performed in a fume hood, and operators must wear organic solvent-resistant gloves, goggles, and respirators. Triethylamine has a strong, irritating odor and is a flammable liquid; its addition must be carried out away from open flames and in well-ventilated areas.

[0048] It should be noted that the molar ratio of pentafluorobenzoyl chloride to the phenolic hydroxyl groups in spirofluorene is 0.15 to 0.35:1, preferably 0.20 to 0.30:1. This ratio ensures that only a portion of the phenolic hydroxyl groups in spirofluorene are capped by the pentafluorobenzoate, while the remaining phenolic hydroxyl groups are retained for ester bond linkage in the subsequent polycondensation reaction to form the polymer backbone. The five fluorine atoms in the pentafluorobenzoate capping group form a dense hydrophobic barrier layer on the outer layer of the solidified network, effectively blocking the diffusion path of water molecules to the carbonyl group of the ester bond. This, together with the shielding effect of the hexafluoroisopropyl group on the β-hydroxyl group in step 1, forms a multi-layered fluorinated hydrophobic synergistic system.

[0049] Furthermore, the reaction temperature is preferably 2 to 6°C. This low temperature condition allows pentafluorobenzoyl chloride to selectively react with sterically hindered phenolic hydroxyl groups, avoiding the loss of end-capping control caused by non-selective acylation at room temperature.

[0050] Furthermore, samples can be taken every 15 to 20 minutes during the addition of triethylamine, and the concentration at 3300 to 3500 nm can be monitored using Fourier transform infrared spectroscopy. The attenuation ratio of the absorption peak of the phenolic hydroxyl group in the region was measured. When the conversion rate of the phenolic hydroxyl group reached 20% to 30%, the addition of triethylamine was stopped, and the reaction was immediately cooled to -5 to 0°C to terminate the reaction. This allowed for precise control of the end-capping degree to balance the relationship between hydrophobic properties and the activity of subsequent polycondensation reactions. The conversion rate of the phenolic hydroxyl group was quantitatively calculated using Fourier transform infrared spectroscopy, and the calculation formula was as follows: ,in The conversion rate of phenolic hydroxyl groups. 3300 to 3500 before the reaction Integral area of ​​the phenolic hydroxyl absorption peak in the region This represents the integral area of ​​the phenolic hydroxyl absorption peak at the sampling time.

[0051] Furthermore, during the solid dissolution stage, the stirring speed is 200 to 300 rpm, the dissolution temperature is 20 to 25°C, and the stirring time is 30 to 60 min until the system becomes clear. The cooling rate to the target reaction temperature is 1 to 3°C / min, with continuous stirring during the cooling process, and the stirring speed is maintained at 200 to 300 rpm.

[0052] Furthermore, the triethylamine hydrochloride filter cake obtained from step 5 must be washed 1 to 2 times with a small amount of cold anhydrous dichloromethane (0 to 5°C). The washing liquid should be added to the filtrate and subjected to vacuum distillation together to reduce product loss. The fluorinated end-capped spirocyclic diol intermediate obtained after removing anhydrous dichloromethane by vacuum distillation is a light yellow to white solid or viscous substance. It must be stored in a sealed container under nitrogen protection at a temperature not exceeding 10°C to prevent oxidation and discoloration of residual phenolic hydroxyl groups.

[0053] Furthermore, the anhydrous dichloromethane vapor recovered by vacuum distillation in step 5 must be recovered via a condenser. The recovered anhydrous dichloromethane can be recycled after drying with a molecular sieve. The triethylamine hydrochloride solid waste obtained from filtration must be collected in a sealed container and disposed of by a professional waste treatment facility; it must not be discarded arbitrarily. Washing waste liquid containing anhydrous dichloromethane must be collected separately and disposed of in accordance with the regulations for the treatment of halogenated hydrocarbon organic waste liquid.

[0054] Step 6: Cocondensation reaction 60 to 90 parts by weight of the fluorinated end-capped spirocyclic biphenol intermediate obtained in step 5, 30 to 55 parts by weight of the fluorinated cyclic carbonate end-capped diester intermediate obtained in step 4, 50 to 80 parts by weight of isophthalic acid (purity ≥99.5%), and 0.5 to 1.5 parts by weight of tetrabutyl titanate are added to mesitylene solvent. The amount of mesitylene is 2 to 4 times the total mass of the above solid materials. After stirring until the solids are completely dissolved, nitrogen gas is introduced for protection. The copolymerization reaction is carried out at 180 to 210°C for 7 to 12 hours under nitrogen protection, and the condensation byproducts are continuously distilled off.

[0055] Furthermore, the preferred co-condensation reaction temperature is 190 to 200°C, and the preferred reaction time is 9 to 11 hours. When the fluorinated cyclic carbonate-terminated diester intermediate participates in the polycondensation, the cyclic carbonate groups at both ends do not participate in the transesterification reaction but remain at the polymer chain ends, serving as active sites for autocatalytic cooling curing during subsequent curing. The preferred amount of tetrabutyl titanate is 0.8 to 1.2 parts by weight. This range ensures the polycondensation reaction rate while avoiding unintended side reactions of the cyclic carbonate groups catalyzed by excessive tetrabutyl titanate during subsequent curing.

[0056] It should be noted that in fluorinated end-capped spirobicyclophenol intermediates, because some of the phenolic hydroxyl groups have been capped by pentafluorobenzoate, only the remaining phenolic hydroxyl groups participate in the polycondensation reaction. Since the pentafluorobenzoate group is directly linked to the spirobifluorene backbone, the fluorinated component is dispersed in the polymer backbone in the form of chemical bonds, avoiding the microphase separation problem caused by differences in solubility parameters when the fluorinated monomer directly participates in polycondensation as a free comonomer.

[0057] Furthermore, a programmed temperature ramp can be used for the co-condensation reaction: first, the reaction is carried out at 180 to 185°C for 2 to 3 hours to complete the pre-condensation stage, allowing oligomers to form and establishing a homogeneous reaction system; then, the temperature is increased to 195 to 210°C for 5 to 8 hours to complete the deep condensation. This programmed temperature ramp avoids the local oligomerization and gelation caused by large differences in monomer concentration in the early stage of one-step high-temperature condensation, further improving the molecular weight uniformity of the condensation product.

[0058] Furthermore, the heating rate during the pre-polymerization stage, from 180 to 185°C, is 1 to 2°C / min, while the heating rate during the deep polymerization stage, from 185°C to 195 to 210°C, is 0.5 to 1.0°C / min. Throughout the polymerization process, the nitrogen flow rate is 0.05 to 0.10 L / min, and the stirring speed is 150 to 250 rpm. Condensation byproducts are continuously discharged through a water separator connected to the reactor. The water separator temperature is maintained at 110 to 120°C to ensure reflux of mesitylene and separation of byproducts.

[0059] Furthermore, tetrabutyl titanate must be pre-dissolved in a small amount of mesitylene to prepare a homogeneous solution with a mass fraction of 5 to 10% before being added to the reaction system to ensure that tetrabutyl titanate is uniformly dispersed in the system and to avoid side reactions caused by excessively high local catalyst concentrations.

[0060] Furthermore, mesitylene is a flammable organic solvent (flash point 48°C). When operating step 6 at a high temperature of 180 to 210°C, the reaction system must be strictly sealed and carried out under nitrogen protection. Open flames are prohibited in the reaction area, and heating equipment must have over-temperature protection. The condensation byproduct vapors and a small amount of mesitylene vapors emitted from the polycondensation reaction must be recovered via a condenser, and uncondensed gases must be adsorbed by activated carbon before being released. Waste catalyst residue containing tetrabutyl titanate must be collected as heavy metal-containing solid waste and disposed of by a professional organization.

[0061] Step 7: Subsequent product refining The polycondensation product obtained in step 6 is cooled to 90 to 120°C and diluted with mesitylene to a solid content of 58 to 65 parts by weight per 100 parts by weight. Insoluble impurities and gel particles are removed by 1 to 3 μm precision filtration, and the product is degassed at 50 to 70°C and a vacuum of -0.085 to -0.098 MPa for 1 to 2 h to obtain the active ester curing agent.

[0062] Furthermore, the pore size of the filter membrane for precision filtration is preferably 1.5 to 2.0 μm. The degassing temperature is preferably 55 to 65°C, which allows the viscosity of the active ester curing agent to decrease to a suitable operating range while avoiding excessive temperature that could lead to the decomposition of cyclic carbonate groups. The final product has a solid content of 58 to 65 parts by weight per 100 parts by weight, a viscosity of 3000 to 8000 mPa·s at 25°C, and a weight-average molecular weight of 8000 to 15000 g / mol.

[0063] Furthermore, the solid content of the final product was determined by thermogravimetric analysis. Approximately 1 g of sample was dried in an oven at 105°C until constant weight. The formula for calculating the solid content is as follows: ,in For solid content, This refers to the sample mass before drying. The mass of the sample is the mass after drying to constant weight. Viscosity at 25°C was determined using a rotational viscometer. Weight-average molecular weight was determined by gel permeation chromatography (GPC) using anhydrous tetrahydrofuran as the mobile phase and narrow-distribution polystyrene as the standard sample for calibration.

[0064] Furthermore, the polycondensation product obtained in step 6 is cooled from 180 to 210°C to 90 to 120°C at a cooling rate of 2 to 5°C / min, with continuous stirring during the cooling process at a speed of 100 to 200 rpm to prevent the polycondensation product from precipitating solids due to localized supercooling during cooling. The degassing operation employs an intermittent vacuum method, maintaining vacuum for 10 to 15 minutes each time followed by 5 minutes of vacuum release, repeating this cycle until the total degassing time reaches 1 to 2 hours. After degassing is complete, the vacuum is released to atmospheric pressure using nitrogen.

[0065] Furthermore, the retention rate of cyclic carbonate groups in the final obtained reactive ester curing agent was determined by Fourier transform infrared spectroscopy, ranging from 1800 to 1820 nm. The ratio of the integrated area of ​​the characteristic absorption peak of the carbonyl group of the cyclic carbonate to the internal standard peak is used for characterization, and the calculation method is the same as described in step 3. The number-average molecular weight and molecular weight distribution index of the reactive ester curing agent are determined simultaneously by gel permeation chromatography. The residual tricresyl content in the reactive ester curing agent is determined by gas chromatography (GC), and the residual solvent content must be less than 1000 ppm.

[0066] Furthermore, insoluble impurities and gel particles trapped by precision filtration must be collected and disposed of as solid waste. Mestriol vapor extracted during degassing must be recovered via a condenser; the recovered mestriol can be recycled for dilution operations in step 6 or step 7, thereby improving solvent utilization and reducing organic solvent waste.

[0067] In step 1 of this invention, a fluorinated bicyclic carbonate monomer is prepared using 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether as a raw material. This allows the β-hydroxyl group generated during the subsequent curing process to be directly adjacent to the hexafluoroisopropyl group. The strong electron-withdrawing effect of the hexafluoroisopropyl group weakens the hydrogen bond donor ability of the β-hydroxyl group. The perfluorocarbon chain forms a hydrophobic shield for the hydroxyl group in space, suppressing the hydrophilicity of the cyclic carbonate ring-opening product at the molecular level. This allows the active ester curing agent to retain the self-catalytic cooling curing function of the cyclic carbonate while suppressing the hygroscopicity of the cured product.

[0068] In step 3 of this invention, a microchannel reactor is used for continuous acylation. Its extremely high specific surface area heat transfer characteristics control the temperature gradient in the reaction area within ±1℃. Compared with the local temperature gradient of 15 to 25℃ during the scale-up of the batch batch process, this effectively avoids the thermal decomposition of cyclic carbonate groups due to local overheating, thereby improving the batch-to-batch consistency of the retention rate of cyclic carbonate groups in the product.

[0069] In step 5 of this invention, pentafluorobenzoyl chloride selectively caps some of the phenolic hydroxyl groups of spirodifluorene. The pentafluorobenzoate groups are chemically bonded to the spirodifluorene backbone and participate in polycondensation, ensuring that the fluorinated component is uniformly dispersed in the polymer backbone. This avoids microphase separation caused by differences in solubility parameters when fluorinated monomers are directly polycondensed as free comonomers. Simultaneously, the pentafluorobenzoate capping groups form a fluorinated hydrophobic barrier layer on the outer layer of the cured network. Together with the intramolecular shielding of the β-hydroxyl group by hexafluoroisopropyl in step 1, this constitutes a multi-layered fluorinated hydrophobic structure, further inhibiting the adsorption of moisture by the cured product and improving the dielectric loss stability of the cured product under high temperature and high humidity conditions.

[0070] Furthermore, in step 4, the present invention recovers N,N-diisopropylethylamine through alkali extraction; in steps 4 and 7, the organic solvent is recovered and recycled through condensation; and in step 5, anhydrous dichloromethane is recovered and recycled. This demonstrates the environmental advantages of raw material recycling and waste reduction, and reduces the total consumption of organic solvents and waste emissions during the production process.

[0071] Example 1 Step 1: Dissolve 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether (epoxy value 0.53 eq / 100g, number-average molecular weight 470 g / mol, viscosity at 25℃ 1200 mPa·s) in 200 parts by weight of anhydrous N,N-dimethylacetamide. After purging the reaction system with nitrogen three times, use ethylene glycol aqueous solution as the cooling medium to control the reactor temperature, and stir at 200 rpm for 30 min to... The pressure inside the reactor was steadily increased to 2 MPa. Three parts by weight of tetrabutylammonium bromide were added, and the reaction was carried out at 100°C for 8 h to complete the cyclization addition. After the reaction, anhydrous N,N-dimethylacetamide was removed by vacuum distillation at -0.085 MPa and 80°C. The crude product was dissolved in ethyl acetate and then cooled to 0°C at a rate of 0.5°C / min in a fume hood to crystallize. The crystals were collected by filtration, washed twice with cold ethyl acetate at 0°C (each time with an amount equal to the mass of the crystals), and dried to constant weight in a 40°C oven to obtain a fluorinated bicyclic carbonate monomer (denoted as intermediate A1). The cyclization addition conversion rate was determined using the following formula: ,in This represents the integrated area of ​​the characteristic peak of the epoxy group before the reaction. The integral area of ​​the characteristic peak of the epoxy group after the reaction was measured. It is 88.2%.

[0072] Step 2: Under stirring at 20℃ and 200 rpm, dissolve intermediate A1 in anhydrous tetrahydrofuran to prepare material A with a concentration of 30 parts by weight / 100 parts by weight, and stir for 20 min until clear; dissolve 2,6-naphthalenedicarboxyl chloride in anhydrous tetrahydrofuran to prepare material B with a concentration of 20 parts by weight / 100 parts by weight, and stir for 20 min until clear; dissolve N,N-diisopropylethylamine in anhydrous tetrahydrofuran to prepare material C with a concentration of 10 parts by weight / 100 parts by weight, and stir for 20 min until clear. Store all materials in sealed containers protected from light for later use.

[0073] Step 3: Materials A, B, and C are simultaneously injected into a microchannel reactor with an inner diameter of 1 mm using a precision metering pump (T-type first mixing point, second mixing point located 5 mm downstream of the first mixing point). The molar ratio of fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate is 2.1:1, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate is 2.2:1. The reaction temperature is -5℃ (cooling bath temperature set to -8℃), and the residence time is 40 s. The tail gas is absorbed by a 5% (w / w) sodium hydroxide aqueous solution. The outlet material is continuously collected in a nitrogen-covered container to obtain the fluorinated cyclic carbonate-terminated naphthalenedicarboxylate reaction solution. The solution is analyzed by FTIR using the formula... Determination of cyclic carbonate group retention rate ( From 1800 to 1820 The integral area of ​​the characteristic peak. (Integral area of ​​the internal standard peak), measured It is 95.1%.

[0074] Step 4: The reaction solution was washed three times with deionized water (each time using 0.5 times the volume of the organic phase, washing temperature 20℃, and standing for at least 15 min to separate the layers) until the pH of the aqueous phase reached 6, then the organic phase was separated. The organic phase was dehydrated using an anhydrous magnesium sulfate packed column and then fed into a thin-film evaporator to remove anhydrous tetrahydrofuran under a vacuum of -0.085 MPa and a temperature of 45℃ (condensation recovery temperature -10℃), yielding a fluorinated cyclic carbonate-terminated diester intermediate (denoted as intermediate B1). The amine-containing saline phase was alkalized to pH 10 and then extracted with ethyl acetate to recover N,N-diisopropylethylamine. The remaining aqueous phase was neutralized to pH 6 and disposed of according to waste liquid procedures.

[0075] Step 5: Add 60 parts by weight of spirobiflumezol and 8 parts by weight of pentafluorobenzoyl chloride to anhydrous dichloromethane (3 times the mass of spirobiflumezol). Stir at 200 rpm for 30 min under nitrogen protection at 20°C and a nitrogen flow rate of 0.05 L / min until the solid is completely dissolved. After cooling to 0°C at a rate of 1°C / min, add triethylamine (molar ratio of 1.0:1 to pentafluorobenzoyl chloride) dropwise over 0.5 h using a constant pressure dropping funnel. Take samples every 15 min and monitor the conversion rate of the phenolic hydroxyl groups using FTIR (calculated using the formula...). , 3300 to 3500 before the reaction Integral area of ​​the phenolic hydroxyl absorption peak in the region (where the area of ​​the absorption peak at the sampling time is the integral area) when The reaction was terminated by immediately cooling to -5°C when the concentration reached 20%. The molar ratio of pentafluorobenzoyl chloride to phenolic hydroxyl group was 0.15:1. Triethylamine hydrochloride was removed by filtration, and the filter cake was washed once with anhydrous dichloromethane at 0°C. The washing liquid was added to the filtrate, and the anhydrous dichloromethane was removed by vacuum distillation at 40°C and a vacuum degree of -0.085 MPa to obtain a fluorinated end-capped spirocyclic diol intermediate (denoted as intermediate C1), which was then sealed and stored under nitrogen protection.

[0076] Step 6: Add 60 parts by weight of intermediate C1, 30 parts by weight of intermediate B1, 50 parts by weight of isophthalic acid, and 0.5 parts by weight of tetrabutyl titanate (pre-dissolved in mesitylene to prepare a 5% homogeneous solution) to mesitylene (the amount used is twice the total mass of solids). Stir until completely dissolved, and purge with nitrogen (flow rate 0.05 L / min) for protection. Increase the temperature to 180°C at a rate of 1°C / min for pre-polymerization for 2 hours; then increase the temperature to 195°C at a rate of 0.5°C / min for deep polymerization for 5 hours, stirring at 150 rpm, and continuously discharge condensation byproducts at a water separator temperature of 110°C. The total polymerization time is 7 hours.

[0077] Step 7: The polycondensation product was cooled to 90°C at a rate of 2°C / min and diluted with mesitylene at 100 rpm to a solid content of 58 parts by weight / 100 parts by weight. After precision filtration through a 1 μm pore size filter membrane, it was intermittently degassed under vacuum at 50°C and a vacuum degree of -0.085 MPa (single vacuuming for 10 min, followed by vacuum breaking for 5 min, repeated until a total degassed time of 1 h). The vacuum was broken to atmospheric pressure with nitrogen to obtain active ester curing agent sample 1. Solid content ( This refers to the sample mass before drying. The mass of the sample after drying to constant weight was determined to be 58.3%, the viscosity at 25℃ was 3450 mPa·s, the weight-average molecular weight was 8300 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The content of 93.8% was determined by GC to be 620 ppm.

[0078] Example 2 The parameters for steps 1 to 7 use intermediate values ​​(preferably the optimal values).

[0079] Step 1: Dissolve 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether with an epoxy value of 0.55 eq / 100g, a number-average molecular weight of 480 g / mol, and a viscosity of 1500 mPa·s at 25℃ in 250 parts by weight of anhydrous N,N-dimethylacetamide. Stir at 250 rpm for 45 min to... The pressure was increased to 2 MPa, and 4.5 parts by weight of tetrabutylammonium bromide were added. The reaction was carried out at 110 °C for 11 h. Vacuum distillation was performed under reduced pressure of -0.090 MPa and 90 °C. The mixture was cooled to 2.5 °C at a rate of 0.75 °C / min to induce crystallization. The crystals were washed twice with cold ethyl acetate at 2.5 °C (each time using 1.5 times the mass of the crystals), and dried at 45 °C to constant weight to obtain intermediate A2. Determine conversion rate It is 93.6%.

[0080] Step 2: Prepare material A (concentration 35 parts by weight / 100 parts by weight), material B (concentration 25 parts by weight / 100 parts by weight), and material C (concentration 12 parts by weight / 100 parts by weight) separately at 22.5℃ and 300 rpm, and stir each for 30 min until clear.

[0081] Step 3: A 1.5 mm inner diameter microchannel reactor was used. The molar ratio of fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride was 2.2:1, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride was 2.5:1. The reaction temperature was 1.5℃ (cooling bath temperature -2.5℃), the residence time was 60 s, and the second mixing point was located 10 mm downstream of the first mixing point. The exhaust gas was absorbed by a 7.5% (w / w) sodium hydroxide aqueous solution. The retention rate of the cyclic carbonate groups was determined by FTIR. It is 96.8%.

[0082] Step 4: Wash four times with deionized water (each time using 0.75 times the volume of the organic phase, washing temperature 25℃, allowing to stand for at least 15 min to separate the phases) until the pH of the aqueous phase reaches 6.5, then separate the organic phase. The organic phase is dehydrated using an anhydrous magnesium sulfate packed column, and then anhydrous tetrahydrofuran is removed using a thin-film evaporator at a vacuum of -0.090 MPa and a temperature of 48℃ (condensation recovery temperature -5℃). The amine-containing saline phase is alkalized to pH 11 and then N,N-diisopropylethylamine is recovered by extraction with ethyl acetate. The remaining aqueous phase is neutralized to pH 7 and disposed of according to waste liquid procedures. Intermediate B2 is obtained.

[0083] Step 5: Mix 75 parts by weight of spirobifluocinol and 13 parts by weight of pentafluorobenzoyl chloride, using anhydrous dichloromethane at a ratio of 4.5 times the mass of spirobifluocinol. Stir at 250 rpm, 22.5°C, and nitrogen flow rate of 0.075 L / min for 45 min until dissolved. Cool to 2°C at a rate of 2°C / min, and add triethylamine (molar ratio of 1.25:1 to pentafluorobenzoyl chloride) dropwise over 0.75 h, taking samples every 17.5 min for monitoring. When the concentration reaches 25%, the temperature is lowered to -2.5℃ to terminate the process. The molar ratio of pentafluorobenzoyl chloride to phenolic hydroxyl group is 0.20:1. Triethylamine hydrochloride is removed by filtration. The filter cake is washed once with anhydrous dichloromethane at 2.5℃. The washing liquid is added to the filtrate. The solvent is removed by vacuum distillation at 45℃ and a vacuum degree of -0.090 MPa to obtain intermediate C2, which is then sealed and stored under nitrogen protection.

[0084] Step 6: Prepare a 7.5% (w / w) solution of intermediate C2 (75 parts by weight), intermediate B2 (42.5 parts by weight), isophthalic acid (65 parts by weight), and tetrabutyl titanate (0.8 parts by weight). The amount of mesitylene used is three times the total mass of the solids. The nitrogen flow rate is 0.075 L / min, and the stirring speed is 200 rpm. The temperature is increased to 182.5℃ at a rate of 1.5℃ / min for pre-polymerization for 2.5 h; then increased to 202.5℃ at a rate of 0.75℃ / min for deep polymerization for 6.5 h. The water separator temperature is 115℃. The total polymerization time is 9 h.

[0085] Step 7: Cool to 105℃ at a rate of 3.5℃ / min, dilute to a solid content of 61.5 parts by weight / 100 parts by weight with stirring at 150 rpm, filter through a 1.5 μm pore size filter membrane, and degas intermittently under vacuum at 55℃ and a vacuum degree of -0.092 MPa (single vacuuming for 12.5 min, vacuum breaking for 5 min, repeated until a total degassing time of 1.5 h), then break the vacuum to atmospheric pressure with nitrogen to obtain active ester curing agent sample 2. The solid content was determined to be 61.7%, the viscosity at 25℃ was 5280 mPa·s, the weight-average molecular weight was 11200 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The percentage was 97.1%, and the residual trimethylbenzene content was 430 ppm.

[0086] Example 3 The parameters for steps 1 through 7 use the maximum endpoint value.

[0087] Step 1: Dissolve 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether (epoxy value 0.58 eq / 100g, number average molecular weight 490 g / mol, viscosity at 25℃ 1800 mPa·s) in 300 parts by weight of anhydrous N,N-dimethylacetamide. Stir at 300 rpm for 60 min to... The pressure was increased to 5 MPa, and 6 parts by weight of tetrabutylammonium bromide were added. The reaction was carried out at 130 °C for 14 h. Vacuum distillation was performed under reduced pressure of -0.095 MPa and 100 °C. The mixture was cooled to 5 °C at a rate of 1.0 °C / min to crystallize. The crystals were washed three times with cold ethyl acetate at 5 °C (each time with twice the mass of the crystals), and dried at 50 °C to constant weight to obtain intermediate A3. Determine conversion rate It is 91.8%.

[0088] Step 2: Prepare material A (concentration 40 parts by weight / 100 parts by weight), material B (concentration 30 parts by weight / 100 parts by weight), and material C (concentration 15 parts by weight / 100 parts by weight) separately at 25℃ and 400 rpm, and stir each for 40 min until clear.

[0089] Step 3: A 3 mm inner diameter microchannel reactor was used. The molar ratio of fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride was 2.4:1, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride was 2.8:1. The reaction temperature was 8°C (cooling bath temperature 3°C), the residence time was 150 s, and the second mixing point was located 15 mm downstream of the first mixing point. The tail gas was absorbed by a 10% (w / w) sodium hydroxide aqueous solution. The retention rate of the cyclic carbonate groups was determined by FTIR. It is 95.6%.

[0090] Step 4: Wash five times with deionized water (each time using 1.0 times the volume of the organic phase, washing temperature 30℃, allowing standing for at least 15 min to separate the phases) until the pH of the aqueous phase reaches 7, then separate the organic phase. The organic phase is dehydrated using an anhydrous magnesium sulfate packed column, and then anhydrous tetrahydrofuran is removed using a thin-film evaporator at a vacuum of -0.095 MPa and a temperature of 55℃ (condensation recovery temperature 0℃). The amine-containing saline phase is alkalized to pH 12 and then N,N-diisopropylethylamine is recovered by extraction with ethyl acetate. The remaining aqueous phase is neutralized to pH 8 and disposed of according to waste liquid procedures. Intermediate B3 is obtained.

[0091] Step 5: Mix 90 parts by weight of spirobifluocinol and 18 parts by weight of pentafluorobenzoyl chloride, using anhydrous dichloromethane at a ratio of 6 times the mass of spirobifluocinol. Stir for 60 min at 300 rpm, 25°C, and nitrogen flow rate of 0.10 L / min until dissolved. Cool to 10°C at a rate of 3°C / min, and add triethylamine (molar ratio of 1.5:1 to pentafluorobenzoyl chloride) dropwise over 1 h, taking samples every 20 min for monitoring. When the concentration reaches 30%, the temperature is lowered to 0°C to terminate the process. The molar ratio of pentafluorobenzoyl chloride to phenolic hydroxyl group is 0.35:1. Triethylamine hydrochloride is removed by filtration. The filter cake is washed twice with anhydrous dichloromethane at 5°C. The washing liquid is combined with the filtrate. The solvent is removed by vacuum distillation at 50°C and a vacuum degree of -0.095 MPa to obtain intermediate C3, which is then sealed and stored under nitrogen protection.

[0092] Step 6: Prepare a 10% (w / w) solution of intermediate C3 (90 parts by weight), intermediate B3 (55 parts by weight), isophthalic acid (80 parts by weight), and tetrabutyl titanate (1.5 parts by weight). The amount of mesitylene used is 4 times the total mass of the solids. The nitrogen flow rate is 0.10 L / min, and the stirring speed is 250 rpm. Pre-polymerize at 185℃ for 3 h by increasing the temperature at 2℃ / min; then further polymerize at 210℃ for 8 h by increasing the temperature at 1.0℃ / min. The water separator temperature is 120℃. The total polymerization time is 11 h.

[0093] Step 7: Cool to 120℃ at a rate of 5℃ / min, dilute to a solid content of 65 parts by weight / 100 parts by weight under stirring at 200 rpm, filter through a 3 μm pore size filter membrane, and intermittently degas under vacuum at 70℃ and a vacuum degree of -0.098 MPa (single vacuuming for 15 min, vacuum breaking for 5 min, repeated until a total degassing time of 2 h), and break the vacuum to atmospheric pressure with nitrogen to obtain active ester curing agent sample 3. The solid content was determined to be 65.1%, the viscosity at 25℃ was 7680 mPa·s, the weight-average molecular weight was 14600 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The content was 96.2%, and the residual trimethylbenzene content was 510 ppm.

[0094] Example 4 In step 1 The pressure was 4 MPa, the reaction temperature was 120℃, and the parameters for step 1 were the same as in Example 2. The parameters for step 2 were the same as in Example 2. In step 3, the inner diameter of the microchannel reactor was 2.0 mm, the molar ratio of the fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride was 2.3:1, and the residence time was 100 s. The parameters for step 3 were the same as in Example 2. In step 4, the temperature of the thin-film evaporator was 52℃. The parameters for step 4 were the same as in Example 2. In step 5, the target cooling temperature was 6℃, the molar ratio of pentafluorobenzoyl chloride to phenolic hydroxyl groups was 0.30:1, and the parameters for step 5 were the same as in Example 2. In step 6, the amount of tetrabutyl titanate was 1.2 parts by weight (prepared into a 7.5% mesitylene solution), the deep polycondensation temperature was 200℃, and the total polycondensation time was 11 h (2.5 h for pre-polymerization and 8.5 h for deep polycondensation). The parameters for step 6 were the same as in Example 2. In step 7, the filter membrane pore size is 2.0 μm and the degassing temperature is 65℃. The other parameters in step 7 are the same as in Example 2.

[0095] Step 1: Dissolve 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether with an epoxy value of 0.55 eq / 100g, a number-average molecular weight of 480 g / mol, and a viscosity of 1500 mPa·s at 25℃ in 250 parts by weight of anhydrous N,N-dimethylacetamide. Stir at 250 rpm for 45 min to... The pressure was increased to 4 MPa, and 4.5 parts by weight of tetrabutylammonium bromide were added. The reaction was carried out at 120 °C for 11 h. The mixture was then subjected to vacuum distillation at -0.090 MPa and 90 °C, and cooled to 2.5 °C at a rate of 0.75 °C / min to induce crystallization. The crystals were washed twice with cold ethyl acetate at 2.5 °C (each time using 1.5 times the mass of the crystals), and dried at 45 °C to constant weight to obtain intermediate A4. Determine conversion rate It is 95.2%.

[0096] Steps 2 and 3: Material preparation is the same as in Example 2. A 2.0 mm inner diameter microchannel reactor was used. The molar ratio of fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride was 2.3:1, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride was 2.5:1. The reaction temperature was 1.5℃ (cooling bath temperature -2.5℃), the residence time was 100 s, the second mixing point was located 10 mm downstream of the first mixing point, and the tail gas was absorbed by a 7.5% (w / w) sodium hydroxide aqueous solution. The retention rate of cyclic carbonate groups was determined by FTIR. It is 97.3%.

[0097] Step 4: The washing operation is the same as in Example 2. The anhydrous tetrahydrofuran is removed by the thin film evaporator at a temperature of 52°C and a vacuum degree of -0.090 MPa to obtain intermediate B4.

[0098] Step 5: Dissolve 75 parts by weight of spirobifluocinol and 13 parts by weight of pentafluorobenzoyl chloride, using anhydrous dichloromethane at a ratio of 4.5 times the mass of spirobifluocinol. Cool the solution to 6°C at a rate of 2°C / min. Maintain a molar ratio of pentafluorobenzoyl chloride to phenolic hydroxyl groups of 0.30:1. Add triethylamine (molar ratio to pentafluorobenzoyl chloride 1.25:1) dropwise over 0.75 h, taking samples every 17.5 min for monitoring. When the temperature reaches 25%, the temperature is lowered to -2.5°C to terminate the process. The post-processing is the same as in Example 2, yielding intermediate C4.

[0099] Step 6: Prepare a 7.5% (w / w) solution of intermediate C4, intermediate B4, 65 (w / w) of isophthalic acid, and 1.2 (w / w) of tetrabutyl titanate. The amount of mesitylene is 3 times the total mass of the solids. The nitrogen flow rate is 0.075 L / min, the stirring speed is 200 rpm, and the temperature is increased to 182.5℃ at 1.5℃ / min for pre-polymerization for 2.5 h. Then, the temperature is increased to 200℃ at 0.75℃ / min for deep polymerization for 8.5 h. The total polymerization time is 11 h. The water separator temperature is 115℃.

[0100] Step 7: Cool to 105℃ at a rate of 3.5℃ / min, dilute to a solid content of 61.5 parts by weight / 100 parts by weight with stirring at 150 rpm, filter through a 2.0 μm pore size filter membrane, and degas intermittently under vacuum at 65℃ and a vacuum degree of -0.092 MPa (single vacuuming for 12.5 min, vacuum breaking for 5 min, repeated until a total degassing time of 1.5 h), then break the vacuum to atmospheric pressure with nitrogen to obtain active ester curing agent sample 4. The solid content was determined to be 61.9%, the viscosity at 25℃ was 5560 mPa·s, the weight-average molecular weight was 11800 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The content was 97.5%, and the residual trimethylbenzene content was 390 ppm.

[0101] Comparative Example 1 Except for step 3, which uses an intermittent batch acylation reaction, the parameters of the other steps are the same as in Example 2.

[0102] Step 3 (Stirred-Bottle Acylation): Materials A, B, and C were added to a jacketed batch reactor at the same molar ratio as in Example 2. The reaction was carried out with stirring at 1.5°C (jacket cooling), and the reaction time was set to the equivalent conversion time required in Example 2 (approximately 30 min). Due to the limited heat transfer during the scale-up of the stirred-bottle process, the measured local temperature gradient inside the reactor was 18°C, exceeding the thermal stability threshold of the cyclic carbonate groups. After discharge, the material was purified in the same step 4 as in Example 2 to obtain a fluorinated cyclic carbonate-terminated diester intermediate (denoted as intermediate B-C1). The retention rate of the cyclic carbonate groups was determined by FTIR. It is 84.3%.

[0103] Steps 5, 6, and 7 are the same as in Example 2, with intermediate B-C1 replacing intermediate B2 in the co-condensation process, yielding the active ester curing agent sample C1. The solid content was measured to be 61.4%, the viscosity at 25°C was 5190 mPa·s, the weight-average molecular weight was 10800 g / mol, and the final product showed a high retention rate of cyclic carbonate groups. The content was 82.7%, and the residual trimethylbenzene content was 450 ppm.

[0104] Comparative Example 2 Except for step 5, which omits pentafluorobenzoyl chloride end-capping and directly uses uncapped spirobifluorene diol in step 6 for co-condensation, the parameters of the remaining steps are the same as in Example 2.

[0105] Step 5 (End-capping omitted): 75 parts by weight of spirobifluorene are directly used in step 6 without pentafluorobenzoyl chloride end-capping treatment, and the phenolic hydroxyl groups remain intact. ), without the introduction of fluorine-containing end-capping groups.

[0106] Step 6: Replace intermediate C2 with 75 parts by weight of uncapped spirobifluorene, with the remaining feed and process parameters the same as in Example 2, to obtain active ester curing agent sample C2. The solid content was determined to be 61.6%, the viscosity at 25℃ was 5350 mPa·s, the weight-average molecular weight was 11000 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The content was 96.9%, and the residual trimethylbenzene content was 440 ppm.

[0107] Comparative Example 3 Except for replacing 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether with bisphenol A glycidyl ether (epoxy value 0.55 eq / 100g, number average molecular weight 480 g / mol, viscosity at 25℃ 1500 mPa·s, without hexafluoroisopropyl bridging structure) in step 1, the parameters of the other steps are the same as in Example 2.

[0108] Step 1: Dissolve 100 parts by weight of bisphenol A glycidyl ether in 250 parts by weight of anhydrous N,N-dimethylacetamide, and stir at 250 rpm for 45 minutes. The pressure was increased to 2 MPa, and 4.5 parts by weight of tetrabutylammonium bromide were added. The mixture was reacted at 110°C for 11 h. The post-treatment was the same as in Example 2, and a fluorine-free bicyclic carbonate monomer (denoted as intermediate A-C3) was obtained. Determine conversion rate It is 93.1%.

[0109] Steps 2 to 7 use the same parameters as in Example 2, except that intermediate A2 is replaced by intermediates A-C3 to obtain the active ester curing agent sample C3. The solid content was measured to be 61.5%, the viscosity at 25°C was 5230 mPa·s, the weight-average molecular weight was 11100 g / mol, and the retention rate of cyclic carbonate groups was [not specified]. The content was 96.7%, and the residual trimethylbenzene content was 460 ppm.

[0110] Experimental test: Using the active ester curing agents prepared in Examples 1 to 4 as the research object, the following three sets of control experiments were conducted to verify the following: (1) The effect of microchannel continuous acylation process (step 3) on the retention rate of cyclic carbonate groups and batch-to-batch consistency (comparison between Example 2 and Comparative Example 1). (2) The contribution of pentafluorobenzoate end-capping structure (step 5) to the hydrophobicity of the cured product and the dielectric loss stability under high temperature and high humidity conditions (comparison between Example 2 and Comparative Example 2). (3) Effect of hexafluoroisopropyl bridging structure (step 1) on the water absorption rate and high temperature and high humidity dielectric stability of the cured product (comparison between Example 2 and Comparative Example 3).

[0111] Experimental sample preparation: The active ester curing agent solutions obtained in each example and comparative example were uniformly mixed with 4,4'-diaminodiphenylmethane (the amount was calculated based on the ratio of active hydrogen equivalent to active ester equivalent of 1:1), and cured in a mold at 150°C for 4 h to prepare cured sample pieces (size 50 mm × 50 mm × 2 mm) for subsequent performance testing.

[0112] Experimental conditions: Water absorption rate test: Performed according to GB / T 1034. The sample was soaked in deionized water at 23℃ for 24 h. The ratio of the mass difference before and after soaking to the mass before soaking is the water absorption rate.

[0113] Dielectric loss test: A vector network analyzer was used, with a test frequency of 10 GHz. The test environment was divided into two conditions: normal temperature and humidity (25℃, 50%RH) and high temperature and high humidity (85℃, 85%RH, sample pretreatment for 96 h).

[0114] Batch consistency of cyclic carbonate group retention: Five batches were prepared consecutively, and the product was determined by FTIR. Value, calculate the standard deviation between batches. ,in , For the first Batch measured values, The mean, This refers to the batch number.

[0115] Curing temperature: The peak curing temperature was determined by differential scanning calorimetry (DSC) at a heating rate of 10℃ / min.

[0116] Experimental steps: Step 1: Prepare the active ester curing agent solution for each sample according to the formulation and process described in Examples 1 to 4 and Comparative Examples 1 to 3.

[0117] Step 2: Following the method described in "Experimental Sample Preparation", the curing agent of each sample is mixed with 4,4'-diaminodiphenylmethane and then cast into a mold. The mixture is cured at 150°C for 4 hours to obtain cured sample pieces. Three pieces are prepared in parallel for each group of samples.

[0118] Step 3: Conduct water absorption rate test, room temperature and humidity dielectric loss test, and high temperature and humidity dielectric loss test on each solidified sample in sequence, and record the data.

[0119] Step 4: FTIR was used to determine the properties of each batch of reactive ester curing agent (represented by 5 batches each prepared in Example 2 and Comparative Example 1). Value, calculate the standard deviation between batches. To evaluate product consistency.

[0120] Step 5: Measure the peak curing temperature of each sample using DSC to confirm the retention of the low-temperature curing function.

[0121] See experimental or test results Figures 2-8 And as shown in the table below: Table 1 Summary of key intermediate process parameters for reactive ester curing agents in each embodiment and comparative example As shown in Table 1, the retention rate of cyclic carbonate groups in step 3 of Examples 1 to 4 is... All were between 95.1% and 97.3% for the final product. The accuracy ranged from 93.8% to 97.5%, demonstrating the stability of the microchannel continuous acylation process across various parameter ranges. Comparative Example 1 (Stirred Tank Acylation) Step 3... The final product was only 84.3%, a decrease of 12.5 percentage points compared to Example 2. The percentage decreased to 82.7%, demonstrating the significant effect of microchannel technology on the retention of cyclic carbonate groups. The final products of Comparative Examples 2 and 3... Similar to Example 2, this indicates that the performance difference between the two and Example 2 is mainly reflected in the hydrophobic properties of the cured product, rather than in the retention rate of cyclic carbonate groups.

[0122] Table 2. Comparison of batch consistency (5 consecutive batches each for Example 2 and Comparative Example 1) As shown in Table 2, Example 2, using a microchannel continuous acylation process, achieved a high retention rate of cyclic carbonate groups in five consecutive batches. inter-batch standard deviation The figure was only 0.15%, while Comparative Example 1 used an intermittent batch acylation process. The result reached 2.08%, indicating that batch-to-batch consistency was significantly worse than in Example 2. Example 2's... The temperature gradient was reduced by 92.8% compared to Comparative Example 1, demonstrating that the microchannel reactor effectively controlled the temperature gradient within ±1℃, thus suppressing batch fluctuations caused by local overheating decomposition of cyclic carbonate groups.

[0123] Table 3. Test results of water absorption rate and curing temperature of cured product As shown in Table 3, the peak curing temperatures of Examples 1 to 4 were all within the range of 152 to 156 °C, demonstrating that the self-catalytic cooling curing function of the fluorinated bicyclic carbonate end-capped structure was retained within all parameter ranges. In Comparative Example 1, due to the low retention rate of cyclic carbonate groups, the peak curing temperature rose to 158 °C, indicating a weakened self-catalytic effect. The water absorption rate of the cured product in Example 2 was 0.31%, while that of Comparative Example 2 (without pentafluorobenzoate end-capping) was 0.57%. Example 2 showed a 45.6% reduction in water absorption compared to Comparative Example 2, demonstrating that the fluorinated hydrophobic barrier layer formed by pentafluorobenzoate end-capping significantly contributes to inhibiting moisture absorption of the cured product. The water absorption rate of Example 2 (0.31%) was 58.1% lower than that of Comparative Example 3 (bisphenol A system, without hexafluoroisopropyl) (0.74%), demonstrating the significant inhibitory effect of the hexafluoroisopropyl bridging structure on moisture absorption of the cured product.

[0124] Table 4. Dielectric loss of cured products under high temperature and high humidity conditions ( Test results (10 GHz) As shown in Table 4, after high temperature and high humidity pretreatment, Examples 1 to 4 showed... Increment The dielectric loss stability was excellent, ranging from 0.0014 to 0.0017. Comparative Example 1, due to its low retention rate of cyclic carbonate groups and insufficient active sites in the cured network, showed poor performance after high temperature and humidity treatment. The value was 0.0028, a 100% increase compared to Example 2, indicating that the retention rate of cyclic carbonate groups has a direct impact on the dielectric stability of the cured product. Comparative Example 2 (without pentafluorobenzoate end-capping) after high temperature and high humidity... The value was 0.0042, a 200% increase compared to Example 2, demonstrating that the hydrophobic barrier layer formed by pentafluorobenzoate end-capping plays a crucial role in blocking the diffusion of moisture to the carbonyl group of the ester bond and suppressing the deterioration of dielectric loss under high temperature and high humidity. Comparative Example 3 (without hexafluoroisopropyl) after high temperature and high humidity... The value was 0.0058, an increase of 314% compared to Example 2, indicating that the hexafluoroisopropyl bridging structure made the most significant contribution to suppressing the deterioration of dielectric loss under high temperature and high humidity. Examples 2 and 4... Both are 0.0014, indicating that their performance is comparable. This demonstrates that within the optimal parameter range, the endpoint values ​​of each parameter can achieve stable dielectric loss control.

[0125] Based on the above experimental results, this invention achieves low hygroscopicity and high-temperature, high-humidity dielectric stability of the cured product through the synergistic effect of three levels of fluorinated hydrophobic structures: Step 1 introduces a hexafluoroisopropyl bridging structure, which reduces the water absorption rate of the cured product by 58.1% compared to the fluorine-free system (Comparative Example 3), and reduces the increase in dielectric loss at high temperature and high humidity by 75.9%; Step 5 introduces a pentafluorobenzoate end-capping structure, which further reduces the water absorption rate from 0.57% (Comparative Example 2) to 0.31% (Example 2) based on Step 1, a reduction of 45.6%, and reduces the increase in dielectric loss at high temperature and high humidity by 66.7%; Step 3, the microchannel continuous acylation process, reduces the standard deviation of the retention rate of cyclic carbonate groups between batches from 2.08% (Comparative Example 1) to 0.15% (Example 2), a reduction of 92.8%, ensuring product consistency and thus ensuring batch stability of curing temperature and dielectric properties. Each embodiment covers all parameter range endpoints and preferred values, all satisfying the requirements of a cured product water absorption rate of less than 0.50% and high-temperature, high-humidity... Performance requirements include an increment of less than 0.0020 and a peak curing temperature of less than 160°C.

[0126] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for preparing an active ester curing agent, characterized in that, Includes the following steps: 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether and A cyclization addition reaction was carried out under the action of a catalyst to obtain a fluorinated bicyclic carbonate monomer. The fluorinated bicyclic carbonate monomer, 2,6-naphthalenedicarboxyl chloride and organic base were respectively prepared into solutions and then simultaneously injected into a microchannel reactor for continuous acylation reaction at -5 to 8°C. After purification, a fluorinated cyclic carbonate-terminated diester intermediate was obtained. Spirobifluorene diol was partially capped by phenolic hydroxyl esterification with pentafluorobenzoyl chloride in the presence of an organic base at 0 to 10 °C to obtain a fluorinated capped spirocyclic diol intermediate. The fluorinated spirocyclic biphenol intermediate, the fluorinated cyclic carbonate-terminated diester intermediate, and isophthalic acid were subjected to a co-condensation reaction at 180 to 210 °C in the presence of an ester exchange catalyst, and the resulting active ester curing agent was obtained after purification.

2. The preparation method according to claim 1, characterized in that, In the cyclization addition reaction, 100 parts by weight of 4,4'-(hexafluoroisopropyl)diphenol glycidyl ether is dissolved in 200 to 300 parts by weight of anhydrous N,N-dimethylacetamide, and the catalyst is tetrabutylammonium bromide, used in an amount of 3 to 6 parts by weight. The pressure was 2 to 5 MPa, the reaction temperature was 100 to 130 °C, and the reaction time was 8 to 14 h. After the reaction was completed, anhydrous N,N-dimethylacetamide was removed by vacuum distillation, and the fluorinated bicyclic carbonate monomer was obtained by recrystallization with ethyl acetate.

3. The preparation method according to claim 1, characterized in that, The fluorinated bicyclic carbonate monomer, 2,6-naphthalenedicarboxylate chloride, and organic base are dissolved in anhydrous tetrahydrofuran to prepare solutions; the inner diameter of the microchannel reactor is 1 to 3 mm, and the residence time of the continuous acylation reaction is 40 to 150 s; the molar ratio of the fluorinated bicyclic carbonate monomer to 2,6-naphthalenedicarboxylate chloride is 2.1 to 2.4:1; the organic base used in the continuous acylation reaction is N,N-diisopropylethylamine, and the molar ratio of N,N-diisopropylethylamine to 2,6-naphthalenedicarboxylate chloride is 2.2 to 2.8:

1.

4. The preparation method according to claim 3, characterized in that, The microchannel reactor inlet adopts a T-type or Y-type mixing structure. After the fluorinated bicyclic carbonate monomer solution and the 2,6-naphthalenedicarboxyl chloride solution merge at the first mixing point, they merge with the N,N-diisopropylethylamine solution at the second mixing point 5 to 15 mm downstream of the first mixing point, thus achieving segmented mixing and feeding.

5. The preparation method according to claim 1, characterized in that, The partial phenolic hydroxyl esterification end-capping is carried out in anhydrous dichloromethane; the molar ratio of pentafluorobenzoyl chloride to spirobifluorene in phenolic hydroxyl groups is 0.15 to 0.35:1; the organic base used in the esterification end-capping is triethylamine, and the molar ratio of triethylamine to pentafluorobenzoyl chloride is 1.0 to 1.5:1; the triethylamine is added dropwise over a period of 0.5 to 1 h, and the reaction is kept at a constant temperature for 1 to 2 h.

6. The preparation method according to claim 1, characterized in that, In the copolymerization reaction, the amount of the fluorinated spirocyclic biphenol intermediate is 60 to 90 parts by weight, the amount of the fluorinated cyclic carbonate-terminated diester intermediate is 30 to 55 parts by weight, and the amount of isophthalic acid is 50 to 80 parts by weight; the transesterification catalyst is tetrabutyl titanate, and the amount is 0.5 to 1.5 parts by weight; the reaction solvent is mesitylene, and the amount is 2 to 4 times the total mass of the solid materials; the copolymerization reaction time is 7 to 12 hours.

7. The preparation method according to claim 6, characterized in that, The co-condensation reaction is carried out using a programmed temperature increase method: first, the reaction is carried out at 180 to 185°C for 2 to 3 hours to complete the pre-condensation, and then the temperature is increased to 195 to 210°C for 5 to 8 hours to complete the deep condensation.

8. The preparation method according to claim 1, characterized in that, The purification process includes: washing the effluent from the continuous acylation reaction with deionized water 3 to 5 times until the pH of the aqueous phase is 6 to 7, separating the organic phase, dehydrating the organic phase with anhydrous magnesium sulfate, and removing the solvent under a vacuum of -0.085 to -0.095 MPa and a temperature of 45 to 55°C to obtain the fluorinated cyclic carbonate-terminated diester intermediate.

9. The preparation method according to claim 1, characterized in that, The refining process includes: cooling the copolymer product to 90 to 120°C, diluting it with mesitylene to a solid content of 58 to 65 parts by weight / 100 parts by weight, filtering it through a filter membrane with a pore size of 1 to 3 μm, and degassing it at 50 to 70°C and a vacuum of -0.085 to -0.098 MPa for 1 to 2 h; the resulting active ester curing agent has a viscosity of 3000 to 8000 mPa·s at 25°C and a weight-average molecular weight of 8000 to 15000 g / mol.

10. An active ester curing agent prepared by the preparation method according to any one of claims 1 to 9.

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