A process for the polymerization of 2,6-dichlorobenzonitrile with mixed dihydric phenols to polyarylene ether nitriles

Abstract

This invention discloses a method and continuous production apparatus for polymerizing polyarylene ether nitrile from 2,6-dichlorobenzonitrile and mixed diphenols, belonging to the field of polymer material synthesis technology. The method includes: mixing 2,6-dichlorobenzonitrile with hydroquinone / bisphenol A at a molar ratio of (0.3~0.7):(0.7~0.3), followed by azeotropic dehydration and step-temperature polycondensation in an alkaline catalyst and organic solvent to obtain a polymer viscous liquid; diluting the viscous liquid and spraying it into a 50%~70% ethanol aqueous solution through a high-pressure nozzle to achieve pressurized spray precipitation; subjecting the precipitated solid to multi-stage hot water washing and continuous vacuum drying using a continuous belt filter to obtain the finished product; recovering the solvent from the mother liquor by distillation; and recycling the wastewater after ultrafiltration membrane treatment. This invention effectively balances the rigidity and solubility of the polymer by controlling the ratio of mixed monomers, and significantly improves the heat and mass transfer efficiency of the high-viscosity system by employing pressurized spray precipitation and continuous washing and drying processes, solving the industry pain points of traditional batch precipitation such as easy agglomeration, high solvent residue, and high water consumption.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis and chemical equipment technology, specifically relating to a method for polymerizing 2,6-dichlorobenzonitrile with mixed diphenols to form polyarylene ether nitrile and its continuous production system. Background Technology

[0002] Polyarylene ether nitrile (PAEN) is a class of special engineering plastics with a main chain containing strongly polar cyano groups and rigid aromatic ether bonds. It possesses excellent thermal stability, dielectric properties, chemical resistance, and mechanical strength, making it irreplaceable in aerospace composite materials, high-frequency electronic packaging substrates, and special separation membranes. Industrially, PAEN is mainly prepared through the nucleophilic aromatic substitution polycondensation reaction of 2,6-dichlorobenzonitrile and diphenols.

[0003] However, existing traditional synthesis processes suffer from the following significant technical bottlenecks: Traditional processes often use single bisphenols. While PAEN synthesized from a single bisphenol A system has a high molecular weight, its chain rigidity and strong crystallization tendency result in extremely high melt viscosity and poor processing fluidity. Meanwhile, the pure hydroquinone system has a low thermal transition temperature, making its heat resistance unsuitable for high-end applications. Direct mixing and feeding often leads to copolymerization sequence segregation due to differences in nucleophilic activity, causing localized phase separation or a broadened molecular weight distribution. The viscosity of the system rises sharply in the later stages of the polycondensation reaction, and the traditional batch precipitation method of "directly pouring the reaction vessel into a water tank" easily causes polymer agglomeration, high internal solvent residue, and uneven precipitate particles. Subsequent washing consumes a large amount of water (usually requiring 8-10 or more washes), and particle adhesion easily occurs during hot water washing. The purity of the dried product is generally below 99.0%, and the high residual solvent content affects the stability of subsequent injection molding or spinning.

[0004] Existing processes typically achieve solvent recovery rates of 70% to 80%, and the presence of oligomers and inorganic salts in the mother liquor leads to scaling in the distillation column. Washing wastewater has a high COD concentration, and there is a lack of efficient membrane separation and circulation systems. Water consumption and waste treatment costs account for more than 30% of the total production cost. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a method and continuous production apparatus for polymerizing polyarylene ether nitrile from 2,6-dichlorobenzonitrile and mixed diphenols. This method balances the rigidity and flexibility of the polymer by controlling the ratio of mixed diphenols, completely solves the mass transfer problem of high-viscosity systems by employing pressurized spray precipitation and continuous washing and drying processes, and achieves a fully green and circular process by combining solvent distillation and ultrafiltration membrane wastewater reuse.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention discloses a method for polymerizing 2,6-dichlorobenzonitrile with a mixture of diphenols to form polyarylene ether nitrile, comprising the following steps: carrying out a nucleophilic substitution polycondensation reaction of 2,6-dichlorobenzonitrile with a mixture of diphenols in the presence of an alkaline catalyst and an organic solvent to obtain a polyarylene ether nitrile polymer viscous; wherein the mixture of diphenols is composed of hydroquinone and bisphenol A mixed in a molar ratio of (0.3~0.7):(0.7~0.3); The reaction mixture was sequentially diluted, pressurized spray sedimentation, solid-liquid separation, continuous washing and drying, solvent recovery and wastewater treatment; The pressurized spray precipitation involves spraying the diluted reaction mixture through a high-pressure nozzle into a 50%~70% volume fraction ethanol aqueous solution for precipitation. The continuous washing and drying process involves washing the precipitated solids 4 to 6 times with hot water at 60°C to 90°C using a continuous belt filter, and then vacuum drying them at 100°C to 130°C for 8 to 12 hours using a continuous vacuum dryer. The polyarylene ether nitrile was prepared with a yield ≥94% and a weight-average molecular weight of 3.5 × 10⁻⁶. 4 ~6.0×10 4 Purity ≥ 99.5%.

[0007] As a preferred technical solution of the present invention, the molar ratio of the mixed diphenols is hydroquinone:bisphenol A = 0.5:0.5. Under this ratio, the copolymer sequence distribution is closest to statistical randomness, which takes into account both heat resistance and melt processing fluidity.

[0008] As a preferred embodiment of the present invention, the alkaline catalyst is potassium carbonate or sodium carbonate, and the molar ratio of the catalyst to 2,6-dichlorobenzonitrile is (1.1~2.4):1, which ensures that the phenolic hydroxyl groups are fully deprotonated and maintains the alkaline reaction microenvironment, effectively suppressing the hydrolysis side reaction of the nitrile group.

[0009] As a preferred embodiment of the present invention, the organic solvent is N-methylpyrrolidone or sulfolane, and the mass ratio of the solvent to 2,6-dichlorobenzonitrile is (5~20):1, which ensures the system uniformity and heat transfer efficiency under high solid content.

[0010] As a preferred technical solution of the present invention, the polycondensation reaction is divided into two stages: azeotropic dehydration at 140℃~180℃ for 2~5 hours to completely remove the water generated in the reaction; and heating to 190℃~240℃ and holding at atmospheric pressure or 0.2~0.5MPa for 4~8 hours.

[0011] As a preferred embodiment of the present invention, N-methylpyrrolidone is added in the dilution step, with a dilution ratio of 1 to 3 times and a temperature of 80°C to 120°C, which effectively reduces the melt viscosity to the atomizable range.

[0012] As a preferred embodiment of the present invention, the spray precipitation pressure is 0.3~1.0MPa, the nozzle orifice diameter is 1~5mm, the volume ratio of precipitant to diluent is (3~5):1, and the precipitation temperature is 25℃~45℃, so as to achieve uniform precipitation at the micron level and completely avoid encapsulation and agglomeration.

[0013] As a preferred technical solution of the present invention, the supporting continuous production device includes a polymerization reactor, a dilution reactor, a high-pressure spray sedimentation tank, a three-stage countercurrent belt filter, a crawler vacuum dryer, a two-component distillation column, and an ultrafiltration membrane wastewater circulation system, realizing closed continuous operation of the entire process.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By using a fast / slow reaction diphenol compound with a ratio of (0.3~0.7):(0.7~0.3), the difference in nucleophilic activity is effectively bridged, and sequence segregation is suppressed; the step-controlled temperature and micro-pressure environment stabilizes the weight-average molecular weight at 3.5×10⁻⁶. 4 ~6.0×10 4 The product combines high heat resistance with excellent melt processability; 2. Pressurized spray sedimentation instantly atomizes high-viscosity viscous liquid into microdroplets, increasing the specific surface area by tens of times. Combined with the rapid desolvation effect of 50%~70% ethanol aqueous solution, it solves the problems of agglomeration and solvent residue caused by traditional pouring methods. Three-stage countercurrent continuous washing ensures that organic solvent residue is <200ppm, polymer purity is stable at ≥99.5%, and yield is increased to 94%~97.5%. Detailed Implementation

[0015] The preferred embodiments of the present invention are described below. 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.

[0016] This invention provides a method and continuous production apparatus for polymerizing polyarylene ether nitrile with 2,6-dichlorobenzonitrile and mixed diphenols.

[0017] The invention is used as follows: 1. Add 2,6-dichlorobenzonitrile, hydroquinone, bisphenol A, potassium carbonate and sulfolane to the polymerization reactor (1), purge with nitrogen and then add toluene, heat to 155℃ and azeotropically remove water for 3 hours. 2. Heat to 210℃ and maintain a micro-positive pressure of 0.3MPa for 5.5 hours to obtain a high-viscosity polymer viscous liquid; 3. The viscous liquid is pumped into the primary dilution vessel (4), diluted twice with NMP (100℃), and sent to the upper part of the sedimentation tank (7) via the high-pressure pump (5). It is then sprayed into a 60% ethanol aqueous solution at 40℃ through a porous atomizing nozzle (6) at 0.6MPa. 4. After solid-liquid separation, the precipitated slurry enters a three-stage countercurrent belt filter (10), is washed five times with 85℃ hot water, and then enters a conveyor vacuum dryer (12) to dry for 10 hours at 115℃ and a vacuum of 0.08MPa to obtain the finished product. 5. The mother liquor enters the distillation tower (13) to separate toluene and NMP for recycling; the washing wastewater is treated by neutralization, activated carbon adsorption and ultrafiltration membrane (18), and the product water is reused in the sedimentation tank and washing area to achieve zero discharge.

[0018] Example 1 In a 50L continuous polymerization reaction system, 5.0 kg (28.98 mol) of 2,6-dichlorobenzonitrile, 1.60 kg (14.53 mol) of hydroquinone, 3.31 kg (14.51 mol) of bisphenol A (molar ratio 0.5:0.5), 4.8 kg (34.7 mol, molar ratio 1.2:1) of anhydrous potassium carbonate, and 35 L of sulfolane were added.

[0019] Under nitrogen protection, 5 L of toluene was added as an azeotropic agent. The temperature was raised to 155 °C and held for 3.0 hours to remove water through azeotropic extraction. The aqueous phase was collected using a separator to the theoretical value. The temperature was then raised to 210 °C at a rate of 1.0 °C / min, and the pressure was maintained at 0.3 MPa for 5.5 hours. The intrinsic viscosity of the system increased to 0.78 dL / g, yielding a polymer viscous solution.

[0020] Pump the slurry into a dilution vessel and add 25L of NMP (diluted twice, temperature 95℃). Turn on the high-pressure pump, adjust the spray pressure to 0.6MPa, and spray into the sedimentation tank through a 6-hole atomizing nozzle (orifice diameter 1.5mm, spray angle 60°). The precipitant is a 60% ethanol-water solution (temperature 35℃), volume ratio 4:1.

[0021] After initial dehydration by a centrifuge, the sediment enters a three-stage countercurrent belt filter. The washing water temperature is 80℃ for the first stage, 85℃ for the second stage, and 90℃ for the third stage, with a spray flow rate of 0.5 m³ / h for each stage, for a total of 5 washes. The wet cake then enters a conveyor-type vacuum dryer and is dried at 115℃ / 0.08 MPa for 10 hours.

[0022] Results: Yield 96.2%, weight-average molecular weight (Mw) 4.8 × 10⁻⁶ 4 PDI=1.72, purity 99.6%, residual solubility <150ppm. The GPC curve shows a unimodal symmetrical distribution.

[0023] Example 2 The ratio of the mixed diphenols was adjusted to hydroquinone:bisphenol A = 0.7:0.3. The catalyst was replaced with sodium carbonate at a molar ratio of 1.5:1. The organic solvent was replaced with NMP at a mass ratio of 8:1. The mixture was heated to 165℃ and held at that temperature for 2.0 hours for azeotropic dehydration. Then, the temperature was increased to 225℃ at a rate of 1.0℃ / min, and the pressure was maintained at 0.4MPa for 4.5 hours. The intrinsic viscosity of the system increased to 0.78 dL / g, yielding the polymer viscous solution.

[0024] Dilution ratio 1.5 times, spray pressure 0.8 MPa, nozzle orifice diameter 1.0 mm. Washing temperature 80℃ / 4 times. Drying 120℃ / 8h.

[0025] Results: Yield 94.8%, Mw = 3.9 × 10⁻⁶ 4 The product has a PDI of 1.68 and a purity of 99.5%. The melt flow rate (MFR, 300°C / 5kg) is approximately 40% higher than that of Example 1, resulting in significantly improved processing fluidity, making it suitable for thin-wall injection molding and precision electronic packaging.

[0026] Example 3 Using the process parameters of Example 1, seven batches were continuously operated (each batch equivalent to a 50L reactor capacity). After separation in a distillation column, NMP and sulfolane were recovered at a rate of 93.5%, and the water content (<50ppm) was directly reused. Washing wastewater (approximately 12m³ / batch) entered a neutralization tank to adjust the pH to 6.5-7.5. After removing trace amounts of phenols and oligomers through activated carbon adsorption, it entered a PVDF hollow fiber ultrafiltration membrane module (membrane pore size 0.03μm, operating pressure 0.25MPa). The product water had a TDS <50mg / L and COD <30mg / L, and was entirely reused in a sedimentation tank for preparing an ethanol-water solution and for spraying with a belt filter.

[0027] Batch 7 product: Yield 95.5%, Mw = 4.6 × 10⁻⁶ 4 PDI=1.74, purity 99.5%. Performance showed no significant degradation compared to the first batch. Fresh water consumption per ton of product decreased from 8.5 tons using the traditional process to 1.8 tons, and organic solvent consumption decreased by 82%.

[0028] Comparative Example 1 The polycondensation reaction conditions were the same as in Example 1. After the reaction was completed, the high-viscosity polymer slurry was directly poured into a large tank containing 80°C deionized water, and the precipitate was manually stirred to break it up. Subsequently, it was filtered through a conventional plate and frame filter press, washed 6 times with 85°C hot water, and vacuum dried at 120°C for 10 hours.

[0029] Results: The precipitate was in the form of irregular large lumps, containing a large amount of sulfolane and toluene. Obvious solvent pores were visible on the cut surface after drying. Yield: 88.4%, Mw = 4.2 × 10⁻⁶ 4However, the purity was only 98.1%, with residual solubility as high as 850 ppm. GPC showed a significant low molecular weight tailing peak (PDI=2.15). This demonstrates the decisive role of pressurized spray precipitation and continuous countercurrent washing in eliminating inclusions and improving purity and molecular weight uniformity.

[0030] Comparative Example 2 Bisphenol A was used only (without hydroquinone), and the proportions of the other raw materials were the same as in Example 1. Stage (a) was performed without toluene azeotropic agent, directly heated to 180°C for 2 hours; Stage (b) was performed at 210°C for 5.5 hours. Post-treatment was the same as in Example 1 (including spray precipitation).

[0031] Results: Due to incomplete water removal and the limited nucleophilic activity of the monomer, the system tended to microgel during the mid-reaction phase, and the nozzle became partially clogged during spraying. Product yield was 82.6%, Mw = 2.8 × 10⁻⁶. 4 The product had a PDI of 2.35 and a purity of 98.7%. Thermogravimetric analysis showed that the Td5% was approximately 25°C lower than in Example 1. This demonstrates the necessity of "toluene azeotropic deep dehydration" and "fast and slow monomer blending" for suppressing side reactions and ensuring high molecular weight and heat resistance.

[0032] Table 1: Comparison of Key Performance and Economic Indicators between Examples and Comparative Examples

[0033] As can be seen from Table 1, all indicators of the method used in this invention are superior to those of the comparative example.

[0034] 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 polymerizing polyarylene ether nitrile with 2,6-dichlorobenzonitrile and mixed diphenols, characterized in that, include: 2,6-Dichlorobenzonitrile and a mixture of diphenols were subjected to a nucleophilic substitution polycondensation reaction in the presence of an alkaline catalyst and an organic solvent to obtain a polyarylether nitrile polymer viscous; the mixture of diphenols was prepared by mixing hydroquinone and bisphenol A in a molar ratio of (0.3~0.7):(0.7~0.3); The reaction mixture obtained after the reaction was completed was successively diluted, pressurized spray precipitation, solid-liquid separation, continuous washing and drying, solvent recovery and wastewater treatment. The pressurized spray precipitation involves diluting the reaction mixture and then spraying it into a precipitant through a high-pressure nozzle. The precipitant is an aqueous ethanol solution with a volume fraction of 50% to 70%. The continuous washing and drying process involves washing the precipitated polyarylether nitrile solid with hot water at 60℃~90℃ 4~6 times in a continuous belt filter, and then vacuum drying it at 100℃~130℃ for 8~12 hours in a continuous vacuum dryer. The yield of the prepared polyarylene ether nitrile was ≥94%, and the weight-average molecular weight was 3.5 × 10⁻⁶. 4 ~6.0×10 4 The polymer purity is ≥99.5%.

2. The method according to claim 1, characterized in that, The molar ratio of the mixed diphenols is hydroquinone:bisphenol A = 0.5:0.

5.

3. The method according to claim 1, characterized in that, The alkaline catalyst is potassium carbonate or sodium carbonate, and the molar ratio of the catalyst to 2,6-dichlorobenzonitrile is (1.1~2.4):

1.

4. The method according to claim 1, characterized in that, The organic solvent is N-methylpyrrolidone or sulfolane, and the mass ratio of the organic solvent to 2,6-dichlorobenzonitrile is (5~20):

1.

5. The method according to claim 1, characterized in that, The nucleophilic substitution condensation reaction includes the following steps: Salt formation reaction stage: 2,6-dichlorobenzonitrile, mixed diphenols, alkaline catalyst and organic solvent are added to the reaction vessel, and toluene, an azeotropic dehydrating agent, is added at the same time. Under the protection of inert gas, the temperature is raised to 140℃~180℃ to carry out the azeotropic dehydration reaction for 2~5 hours. Polymerization reaction stage: The reaction temperature is raised to 190℃~240℃, and the polymerization is carried out under normal pressure or 0.2~0.5MPa pressure for 4~8 hours to obtain polyarylether nitrile polymer viscous.

6. The method according to claim 1, characterized in that, The dilution step involves adding N-methylpyrrolidone to the polyarylene ether nitrile polymer viscous after the polymerization reaction is completed, with a dilution factor of 1 to 3 times the volume of the polymer viscous, and a dilution temperature of 80°C to 120°C.

7. The method according to claim 1, characterized in that, The pressurized spray precipitation process has a spray pressure of 0.3~1.0MPa, a nozzle orifice diameter of 1~5mm, a volume ratio of precipitant to diluted polymer viscous liquid of (3~5):1, and a precipitation temperature of 25℃~45℃.

8. A continuous production system for polyarylether nitrile, characterized in that, Including those connected sequentially according to the process flow: Polymerization reaction unit: including a polymerization reactor with a stirrer, an inert gas inlet and a toluene reflux condenser; Dilution unit: A primary dilution vessel connected to the outlet of the polymerization reactor; Spray sedimentation unit: a high-pressure pump, a high-pressure nozzle, and a sedimentation tank connected to the outlet of the dilution vessel. The high-pressure nozzle is located at the top of the sedimentation tank, and the top of the sedimentation tank is provided with a precipitant inlet. Solid-liquid separation unit: a belt filter or centrifuge connected to the outlet of the sedimentation tank; Washing and drying unit: a continuous belt filter and a continuous vacuum dryer are connected in sequence to the solid outlet of the solid-liquid separation unit; Solvent recovery unit: A distillation column connected to the liquid outlet of the solid-liquid separation unit, the distillation column being equipped with a toluene recovery port and an organic solvent recovery port; Wastewater treatment unit: a neutralization and equalization tank, an activated carbon adsorption tower, and an ultrafiltration membrane separation device are sequentially connected to the bottom drain of the distillation tower. The product water outlet of the ultrafiltration membrane separation device is connected to the sedimentation tank and the washing water inlet of the continuous belt filter.

9. The continuous production system for polyarylene ether nitrile according to claim 8, characterized in that, The high-pressure nozzle is a multi-hole atomizing nozzle with 4 to 12 holes, a nozzle diameter of 0.5 to 2 mm, and a spray angle of 30° to 90°. The continuous belt filter is a three-stage countercurrent washing belt filter, with each washing zone equipped with an independent washing water spray device. The continuous vacuum dryer is a double-cone rotary vacuum dryer or a conveyor belt vacuum dryer with a drying vacuum degree of 0.06 to 0.09 MPa. The ultrafiltration membrane separation device is a hollow fiber ultrafiltration membrane module with a membrane material of polyvinylidene fluoride or polyethersulfone, a membrane pore size of 0.01 to 0.05 μm, and an operating pressure of 0.1 to 0.4 MPa.

10. The use of polyarylene ether nitrile prepared by any one of claims 1-7 in aerospace composite materials, electronic packaging materials or high-temperature resistant films.

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