A method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol
By employing deep pretreatment and a programmed temperature ramping mode for a composite catalytic system, the hydrolysis and solvent recovery issues in the preparation of polyarylether nitrile from 2,6-dichlorobenzonitrile were resolved, achieving efficient and environmentally friendly polymer synthesis and improving product quality and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HUBEI NEW SULAI NEW MATERIAL CO LTD
- Filing Date
- 2026-04-30
- Publication Date
- 2026-06-26
AI Technical Summary
In the existing technology, the preparation of polyarylether nitrile from 2,6-dichlorobenzonitrile involves the entrainment of moisture, ammonia and chlorides, which leads to problems such as hydrolysis of nitrile groups, pipeline blockage and difficulty in solvent recovery, resulting in unstable polymer quality and high environmental pressure.
A deep pretreatment technique is used to remove moisture and chlorides. Combined with a composite catalytic system and a programmed temperature rise mode, a polycondensation reaction with precise molar ratios is carried out. Through multi-stage separation and solvent recovery technology, polyarylether nitrile is synthesized efficiently.
It effectively inhibits nitrile hydrolysis, improves the intrinsic viscosity of the product, shortens the reaction time, reduces production costs, improves solvent recovery efficiency, and meets the needs of different applications.
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Figure CN122277889A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to a method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol, and particularly to a green polycondensation process suitable for gas-phase ammonia oxidation of raw materials, which can effectively inhibit nitrile group hydrolysis and achieve stable preparation of high molecular weight polymers. Background Technology
[0002] Polyarylene ether nitrile (PAEN) exhibits excellent dielectric properties, high-temperature resistance, and chemical corrosion resistance due to the presence of highly polar nitrile groups (-CN) and rigid aromatic ether bonds in its main chain, making it a promising candidate for applications in aerospace, specialty fibers, and electronic packaging materials. Industrially, PAEN is primarily prepared through the nucleophilic aromatic substitution (SNAr) polycondensation reaction of 2,6-dichlorobenzonitrile with diphenols.
[0003] Currently, 2,6-dichlorobenzonitrile is mostly produced by the gas-phase ammonia oxidation of 2,6-dichlorotoluene. Although this process is mature, the product inevitably contains trace amounts of moisture (0.1%~0.3%), unreacted ammonia, and ammonium chloride dust. When such raw materials are used directly for PAEN polycondensation, a series of technical bottlenecks will occur: (1) Moisture reacts with alkaline catalysts to generate a strongly alkaline environment, causing the nitrile group of the polymer main chain to hydrolyze into amides or carboxylic acids, consuming monomers and causing chain termination; (2) Trace amounts of ammonia combine with hydrogen chloride to form crystalline salts, clogging pipes and corroding the inner wall of the reactor; (3) Traditional processes often use a single fluorine / chlorine solvent or excess monomer to compensate for losses, resulting in poor atom economy, difficult post-processing, wide molecular weight distribution (PDI>2.0), and difficulty in efficiently recovering the solvent, resulting in huge environmental pressure.
[0004] Therefore, there is an urgent need to develop a deep pretreatment technology for the characteristics of raw materials in the ammonia oxidation method, combined with precise stoichiometric ratios and a composite catalytic temperature-programmed system, in order to achieve efficient and high-value-added synthesis of polyarylene ether nitrile. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol.
[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:
[0007] This invention discloses a method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol, comprising the following steps: Step S1: Deep pretreatment of raw materials: 2,6-dichlorobenzonitrile raw material and diphenol monomer are placed in a pretreatment reactor, and under the protection of a continuously flowing dry inert gas, a step-by-step heating vacuum degassing process is carried out to remove physically adsorbed moisture, free ammonia and volatile chlorides, to obtain pretreatment intermediate A with a moisture content of less than 50 ppm; Step S2: Composite catalytic polycondensation: In an anhydrous and oxygen-free polymerization reactor, pretreated intermediate A is dissolved in an aprotic polar solvent and a composite catalytic system is added; the reaction system is controlled using a programmed temperature rise mode: first, azeotropic dehydration and pre-polycondensation are carried out at 140~170℃, and then the temperature is raised to 200~240℃ for main chain growth polycondensation reaction, with a reaction time of 4~8 hours, to obtain a reaction slurry B containing polyarylene ether nitrile; Step S3: Precipitation and purification: After cooling the reaction slurry B obtained in step S2, inject it into a non-solvent precipitant, filter and separate to obtain crude polymer and mother liquor C; the crude polymer is subjected to acid washing, hot water washing and Soxhlet extraction with organic solvent to completely remove residual inorganic salts and oligomers, and vacuum drying to obtain polyarylether nitrile product. Step S4: Solvent and by-product recovery: The solvent separated from the mother liquor C is dehydrated by molecular sieve and then recycled for step S2; the separated inorganic salt filter residue is washed and purified and then recovered as a chemical raw material.
[0008] As a preferred embodiment of the present invention, in step S2, the molar ratio of each core raw material is: 2,6-dichlorobenzonitrile: diphenol: inorganic base = 1.00~1.05 : 1.00 : 1.10~1.30; the amount of phase transfer catalyst added in the composite catalytic system is 0.5%~2.0% of the total mass of the reaction system.
[0009] In a preferred embodiment of the present invention, the preferred molar ratio of 2,6-dichlorobenzonitrile to diphenol is 1.02:1.00; the inorganic base is selected from at least one of anhydrous potassium carbonate, anhydrous sodium carbonate, or anhydrous cesium carbonate. The molar ratio of 2,6-dichlorobenzonitrile, diphenol, and inorganic base is strictly controlled at 1.00~1.05 : 1.00 : 1.10~1.30, which effectively suppresses molecular weight capping caused by end-group imbalance through precise metering.
[0010] As a preferred embodiment of the present invention, the phase transfer catalyst is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium chloride, 18-crown-6 or triethylbenzylammonium chloride; the aprotic polar solvent is selected from one or more of sulfolane, N-methylpyrrolidone or dimethyl sulfoxide, and the solid content of the reaction system is controlled at 25% to 40 wt%.
[0011] As a preferred embodiment of the present invention, in step S1, the stepped heating vacuum degassing process specifically involves: first heating to 80-100℃ and holding under vacuum for 1 hour, then heating to 120-150℃ and holding under vacuum for 2-4 hours, with the vacuum level controlled at 0.1-5.0 kPa; the treated material is then deeply purified by passing it through an adsorption column filled with 4A molecular sieve and acid-modified alumina. Step S1 employs a combined vacuum degassing and molecular sieve / acidic alumina dual-stage adsorption technology to reduce the moisture content of the raw material to <50 ppm, completely cutting off the hydrogen source for nitrile hydrolysis.
[0012] As a preferred embodiment of the present invention, the programmed heating mode of step S2 is specifically as follows: First stage: Increase the temperature to 150~165℃ at 1.0~2.0℃ / min, hold for 1.5~3.0 hours, and use a water separator to remove the water generated by the reaction through azeotropic extraction; The second stage involves increasing the temperature at a rate of 0.5–1.2 °C / min to 210–235 °C and holding for 3.0–6.0 hours, thereby increasing the intrinsic viscosity of the polymer to 0.65–0.85 dL / g. Step S2 employs a programmed temperature increase strategy: the low-temperature range (150–165 °C) focuses on dehydration, salt formation, and oligomer formation, while the high-temperature range (210–235 °C) drives chain growth, avoiding cross-linking or degradation caused by localized overheating in the initial high-temperature phase.
[0013] As a preferred embodiment of the present invention, in step S3, the washing process includes: washing with dilute hydrochloric acid with a concentration of 0.1~0.5 mol / L to remove residual metal ions, then washing with boiling water until neutral, and finally Soxhlet extraction with acetone or ethanol for 6~12 hours; the drying temperature is 110~130℃, the vacuum degree is ≤500 Pa, and the drying time is 8~12 hours.
[0014] As a preferred embodiment of the present invention, in step S4, the moisture content of the recovered solvent is controlled below 50 ppm, the number of cycles is ≥8, and the amount of solvent added in a single batch does not exceed 3%; the inorganic salt filter residue is washed with water and dried, and then sold as a potassium / sodium salt by-product or used as agricultural fertilizer.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Deep pretreatment and precise molar ratio result in a nitrile hydrolysis rate of <0.5% and a stable intrinsic viscosity of 0.70~0.85 dL / g, which is more than 25% higher than that of traditional processes; 2. The synergistic effect of inorganic base and phase transfer catalyst significantly reduces the activation energy of SNAr, with a conversion rate of 2,6-dichlorobenzonitrile ≥96.5% and a reaction time shortened by 20%~30%; 3. By adjusting the type of diphenol and process parameters, the rigidity, solubility and thermal stability of the polymer can be flexibly adjusted to meet the needs of differentiated applications; 4. Solvent can be recycled ≥8 times, inorganic salts can be recovered efficiently, and the emission of waste gas, wastewater, and solid waste is reduced by more than 70% compared with traditional processes, and the production cost is reduced by about 18%. 5. The programmed temperature control and two-stage solid-liquid separation design effectively solve the heat and mass transfer problems of high viscosity systems and have the potential for continuous production. Attached Figure Description
[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of the steps of the present invention; Figure 2 This is a comparison curve of the intrinsic viscosity of the product over time under programmed heating and isothermal reaction modes in Example 1. Figure 3 This is a comparison of the intensity of the nitrile peak in the infrared spectra of the products of Comparative Example 1 and Example 1. Detailed Implementation
[0017] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0018] In the attached diagram, all identical reference numerals refer to the same components.
[0019] like Figure 1 As shown, the present invention provides a method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol.
[0020] Example 1: 1.00 kg of 2,6-dichlorobenzonitrile (GC-C) and 0.58 kg of hydroquinone were placed in a pretreatment vessel equipped with a stirring and condensation system. The GC-C contained 0.22% water and <200 ppm ammonia. Nitrogen gas with a dew point of -50°C was introduced, and the mixture was vacuum-treated at 110°C / 1.0 kPa for 3 hours. Subsequently, the material was adsorbed through a 4A molecular sieve column to obtain intermediate A with <40 ppm water and <5 ppm ammonia. A was added to a 20 L polymerization vessel, along with 12 L of sulfolane solvent with <50 ppm water. The mixture was fed at a molar ratio of 2,6-DCBN:hydroquinone:K2CO3 = 1.02:1.00:1.15, and 15 g of tetrabutylammonium bromide (TBAB) phase transfer catalyst was added.
[0021] Under nitrogen protection, the temperature program is started: 1.15℃ / min to 160℃, held for 2.0 hours, and water is removed; 2.1.0℃ / min was increased to 215℃ and held for 5.0 hours to induce polycondensation. During the reaction, the viscosity of the system increased steadily, and no gelation was observed.
[0022] 3. Cooling and precipitation: Cool to 90℃ and slowly inject the reaction solution into 200 L of deionized water to precipitate. Filter to obtain powdered polymer. Wash the filter cake first with 0.1 M HCl, then with boiling water until neutral, and finally extract with methyl ketone using a Soxhlet extractor for 8 h, and dry under vacuum at 120℃.
[0023] 4. A white powder was obtained with a yield of 97.1%, intrinsic viscosity of 0.78 dL / g, PDI of 1.72, and residual chlorine of 98 ppm.
[0024] Example 2: Same as Example 1, except that the raw material was replaced with 0.62 kg of bisphenol A. The molar ratio was adjusted to 2,6-DCBN:bisphenol A:Cs2CO3 = 1.03:1.00:1.20.
[0025] Under nitrogen protection, the temperature program is started: 1.5℃ / min to 160℃, held for 2.5 hours, and water is removed; The temperature was increased to 230℃ at a rate of 0.8℃ / min and held for 5.5 hours to induce polycondensation. The viscosity of the system increased steadily during the reaction, and no gelation was observed. The rest of the process was the same as in Example 1.
[0026] 3. The product yield was 96.4%, the intrinsic viscosity was 0.82 dL / g, and the thermal decomposition temperature Td5% was >490℃.
[0027] It has been demonstrated that increasing the temperature of the second stage can overcome the steric hindrance of the bisphenol A isopropyl group and promote the formation of high molecular weight segments.
[0028] Example 3: Based on Example 1, the mother liquor (containing sulfolane and a small amount of inorganic salts) from the cooling precipitation step was collected. The mother liquor was first subjected to precision filtration to remove polymer particles, and then dehydrated and distilled under reduced pressure in a distillation column. The recovered solvent was treated with a molecular sieve bed, and the moisture content was controlled at 45 ppm. This recovered solvent was used for the next batch of polymerization (batches 2-5). The intrinsic viscosity of the product in batch 5 was 0.71 dL / g, which was not significantly different from that of the fresh solvent (0.74 dL / g), proving that there was no accumulation of impurities or poisoning during solvent recycling.
[0029] Example 4: To clarify the impact of different diphenol structures on polycondensation kinetics and the properties of the final product, under the premise of fixed 2,6-dichlorobenzonitrile feed amount, catalyst system (KF / TBAB composite), and solid content (30 wt%), only the type of diphenol was changed, and the reaction temperature of the second stage was specifically optimized. Key data comparisons are shown in Table 1 below: Table 1
[0030] From an electronic perspective, resorcinol and hydroquinone exhibit strong hydroxyl activation capabilities and rapid polymerization rates. From a steric hindrance perspective, biphenyl and bisphenol A require increased reaction temperatures to overcome steric hindrance and achieve high intrinsic viscosity. From a thermal perspective, biphenyl bisphenol and bisphenol S show significantly improved Tg and Td5% due to the introduction of rigid or strongly polar groups in their main chains. This invention achieves efficient and controllable synthesis of different diphenol systems through precise matching of the temperature-time window.
[0031] Example 5: The process described in Example 1 was continuously run for 5 batches. Each batch of mother liquor was separated in a distillation column and then dehydrated through a 3A molecular sieve bed for direct reuse (water content <45 ppm). The product yield of the 5th batch was 95.8%, with an intrinsic viscosity of 0.75 dL / g and a PDI of 1.74. This demonstrates that the circulating system did not accumulate impurities or suffer from poisoning, and that the process exhibited excellent stability.
[0032] Comparative Example 1: 2,6-Dichlorobenzonitrile was used directly without dehydration treatment, containing 0.22% water. Hydroquinone was added as feedstock, and other conditions were the same as in Example 1. Results: In the initial stage of the reaction, a large amount of nitrile groups hydrolyzed, producing bubbles, and the system color rapidly turned dark brown. After the reaction, the intrinsic viscosity was only 0.41 dL / g, and FT-IR showed 1660 cm⁻¹. - A distinct amide C=O peak appeared at ¹, with residual chlorine reaching 310 ppm. The product was yellow and brittle, unsuitable for high-strength fiber drawing. This fully demonstrates the decisive role of deep dehydration in step S1 in maintaining the reaction stoichiometry and inhibiting hydrolysis.
[0033] Comparative Example 2: The pretreatment was the same as in Example 1, but the molar ratio of feed was adjusted to 2,6-DCBN:hydroquinone:K2CO3 = 0.95:1.00:1.05 (phenol in excess, and no PTC used with only K2CO3). The reaction was carried out at 215℃ for 6 hours. Results: Excess phenol end groups led to premature chain termination, preventing molecular weight growth, and the intrinsic viscosity was 0.38 dL / g. Furthermore, the inorganic salt dispersion was poor, with a large amount of K2CO3 encapsulated in the polymer, making washing extremely difficult, resulting in a final residual chlorine concentration of 520 ppm. This demonstrates the necessity of "micro-excess of haloaromatics + complex phase transfer catalysis" for the synthesis of high molecular weight PAEN.
[0034] Table 2
[0035] As can be seen from Table 1, all parameters in the embodiments are superior to those in the comparative examples.
[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol, characterized in that, Includes the following steps: Step S1: Deep pretreatment of raw materials: 2,6-dichlorobenzonitrile raw material and diphenol monomer are placed in a pretreatment reactor and subjected to step-by-step heating and vacuum degassing under the protection of a continuously flowing dry inert gas to remove physically adsorbed moisture, free ammonia and volatile chlorides, to obtain pretreated intermediate A with a moisture content of less than 50 ppm. Step S2: Composite catalytic polycondensation: In an anhydrous and oxygen-free polymerization reactor, pretreated intermediate A is dissolved in an aprotic polar solvent and a composite catalytic system is added; the reaction system is controlled using a programmed temperature rise mode: first, azeotropic dehydration and pre-polycondensation are carried out at 140~170℃, and then the temperature is raised to 200~240℃ for main chain growth polycondensation reaction, with a reaction time of 4~8 hours, to obtain a reaction slurry B containing polyarylene ether nitrile; Step S3: Precipitation and purification: After cooling the reaction slurry B obtained in step S2, inject it into a non-solvent precipitant, filter and separate to obtain crude polymer and mother liquor C; the crude polymer is subjected to acid washing, hot water washing and Soxhlet extraction with organic solvent to completely remove residual inorganic salts and oligomers, and vacuum drying to obtain polyarylether nitrile product. Step S4: Solvent and by-product recovery: The solvent separated from the mother liquor C is dehydrated by molecular sieve and then recycled for step S2; the separated inorganic salt filter residue is washed and purified and then recovered as a chemical raw material.
2. The method for synthesizing polyarylene ether nitrile using 2,6-dichlorobenzonitrile and diphenol according to claim 1, characterized in that, In step S2, the molar ratio of each core raw material is: 2,6-dichlorobenzonitrile: diphenol: inorganic base = 1.00~1.05 : 1.00 : 1.10~1.30; the amount of phase transfer catalyst added in the composite catalytic system is 0.5%~2.0% of the total mass of the reaction system.
3. The method according to claim 2, characterized in that, The preferred molar ratio of 2,6-dichlorobenzonitrile to diphenol is 1.02:1.00; the inorganic base is selected from at least one of anhydrous potassium carbonate, anhydrous sodium carbonate, or anhydrous cesium carbonate.
4. The method according to claim 2, characterized in that, The phase transfer catalyst is selected from at least one of tetrabutylammonium bromide, tetrabutylammonium chloride, 18-crown-6 or triethylbenzylammonium chloride; the aprotic polar solvent is selected from one or more of sulfolane, N-methylpyrrolidone or dimethyl sulfoxide, and the solid content of the reaction system is controlled at 25% to 40 wt%.
5. The method according to claim 1, characterized in that, In step S1, the step-by-step heating and vacuum degassing process is as follows: first, the temperature is raised to 80~100℃ and held for 1 hour, then the temperature is raised to 120~150℃ and held for 2~4 hours, with the vacuum degree controlled at 0.1~5.0 kPa; the processed material is then deeply purified by an adsorption column filled with 4A molecular sieve and acid-modified alumina.
6. The method according to claim 1, characterized in that, The specific temperature rise mode in step S2 is as follows: First stage: Increase the temperature to 150~165℃ at 1.0~2.0℃ / min, hold for 1.5~3.0 hours, and use a water separator to remove the water generated by the reaction through azeotropic extraction; Second stage: Increase the temperature to 210~235℃ at 0.5~1.2℃ / min and hold for 3.0~6.0 hours to increase the intrinsic viscosity of the polymer to 0.65~0.85 dL / g.
7. The method according to claim 1, characterized in that, In step S3, the washing process includes: washing with dilute hydrochloric acid with a concentration of 0.1~0.5 mol / L to remove residual metal ions, then washing with boiling water until neutral, and finally Soxhlet extraction with acetone or ethanol for 6~12 hours; the drying temperature is 110~130℃, the vacuum degree is ≤500 Pa, and the drying time is 8~12 hours.
8. The method according to claim 1, characterized in that, In step S4, the moisture content of the recovered solvent is controlled below 50 ppm, the number of cycles is ≥8, and the amount of solvent added in a single batch does not exceed 3%; the inorganic salt filter residue is washed with water and dried, and then sold as a potassium / sodium salt by-product or used as agricultural fertilizer.