Synthesis and preparation method of polybenzimidazole resin

Abstract

The invention relates to the technical field of new materials, and particularly discloses a synthetic preparation method of polybenzimidazole resin, which comprises the following steps: step S1, preparing the following raw materials in parts by weight: 3-5 parts of 3, 3 '-diaminobenzidine, 7.8-12.9 parts of functionalized dicarboxylic acid, 500-700 parts of polyphosphoric acid, 28-32 parts of deionized water and 220-240 parts of pH regulator; step S2, synthesizing polybenzimidazole resin; functionalized dicarboxylic acid added in the application contains a pyridine ring, an amino group, a benzene ring, a flexible long-chain alkane structure, an ether bond and trifluoromethyl, the pyridine ring and the amino group can generate hydrogen-bond interaction with a base material and a solvent, the benzene ring has a steric hindrance effect, and the long-chain alkane structure and the ether bond can promote chain segment movement of polybenzimidazole resin, so that the polybenzimidazole resin has a good anti-aging effect. The trifluoromethyl group can improve the hydrophilicity of the polybenzimidazole resin, and through the synergistic effect of the groups, the acid loading level of the polybenzimidazole resin is improved, and the processability of the polybenzimidazole resin is improved.

Description

Technical Field

[0001] The present application relates to the technical field of new materials, and more specifically, to a method for synthesizing and preparing a polybenzimidazole resin. Background Art

[0002] Polybenzimidazole resin is a high-performance engineering resin. Due to its extremely high mechanical properties and excellent thermal stability, it is widely used in aerospace, automobile manufacturing, electronics and other fields.

[0003] The methods for synthesizing polybenzimidazole resins mainly include melt polycondensation, solution polycondensation, matrix synthesis and nucleophilic substitution. Among them, the solution polycondensation method has attracted widespread attention due to its simpler synthesis process, lower reaction conditions and simpler purification technology.

[0004] However, in current technology, the structure of the polybenzimidazole resin prepared by the solution polycondensation method is usually too rigid, the molecular chains are tightly packed, and the processing is difficult, resulting in the prepared polybenzimidazole resin not only having a low acid loading level but also poor thermal stability. Summary of the invention

[0005] In order to solve the problems mentioned in the above background technology, the present application provides a method for synthesizing and preparing a polybenzimidazole resin.

[0006] A method for synthesizing a polybenzimidazole resin comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 3-5 parts of 3,3'-diaminobenzidine, 7.8-12.9 parts of functionalized dicarboxylic acid, 500-700 parts of polyphosphoric acid, 28-32 parts of deionized water and 220-240 parts of pH regulator; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring evenly, gradually heating to 195-215°C under nitrogen protection, and continuing stirring to react for 18-22 hours. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing, and drying to obtain polybenzimidazole resin.

[0007] Preferably, the pH regulator is an aqueous ammonia solution with a mass fraction of 10-20%.

[0008] Preferably, the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically dispersing 6-aminopyridine-2-carboxylic acid in anhydrous DMF, raising the temperature to 55-65° C. while stirring, then adding triethylamine and toluene, and dripping epichlorohydrin, controlling the dripping to be completed within 10 minutes, stirring and reacting for 3-4 hours after the dripping is completed, filtering, rotary evaporation, placing the rotary evaporation product in acetone to dissolve, filtering, rotary evaporation of the filtrate, washing and drying to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23-35:550-640:2.6-3.4:10-14:18-24:16-20, and in the above reaction process, using anhydrous DMF as solvent, triethylamine as catalyst, and toluene as dehydrating agent, the amino group on 6-aminopyridine-2-carboxylic acid and the chlorine atom on epichlorohydrin undergo nucleophilic substitution reaction to obtain an epoxy monomer; The structural formula of the epoxy monomer is shown below:

[0009] Step A2, adding epoxy monomer to anhydrous DMF, heating to 52-56°C, stirring evenly, adding a mixed solution a of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74-80°C, continuing stirring and reacting for 6-10 hours, adjusting the pH to neutral, rotary evaporation, washing and drying to obtain an esterified monomer, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 3-5:65-75:16, and the mass ratio of sebacic acid, tributylamine and isopropanol in the mixed solution a is 3.6-6.2:0.06-0.10:12-14. In the above reaction process, using anhydrous DMF as solvent, the epoxy group on the epoxy monomer undergoes a ring-opening esterification reaction with sebacic acid to obtain an esterified monomer. In the above reaction process, the amount of sebacic acid is controlled to be slightly higher than that of the epoxy monomer so that the epoxy group on it is fully consumed; The structural formula of the esterification monomer is shown below:

[0010] Step A3, add esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir evenly, heat to reflux under nitrogen protection, stir and react for 6-8h, filter and rotary evaporate after the reaction, dissolve the rotary evaporated product in acetone, filter, rotary evaporate the filtrate, wash and dry to obtain functionalized dicarboxylic acid, wherein the mass ratio of esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5-7:2.5-3.5:0.12-0.16:8-12:80-90:36-42, in the above reaction process, with anhydrous DMF as solvent, triethylamine as acid binding agent, toluene as dehydrating agent, the hydroxyl group on the esterification monomer and the active chlorine atom on 1-chloromethyl-3-trifluoromethylbenzene undergo nucleophilic substitution reaction to obtain functionalized dicarboxylic acid. The structural formula of the functionalized dicarboxylic acid is as follows:

[0011] Compared with the prior art, the present invention has the following beneficial effects: In order to increase the acid loading level of the prepared polybenzimidazole resin, reduce its glass transition temperature, and improve its processability, the present application adds a functionalized dicarboxylic acid, which contains a pyridine ring, an amino group, a benzene ring, a flexible long-chain alkane structure, an ether bond, and a trifluoromethyl group. The presence of the pyridine ring and the amino group not only has polarity and hydrophilicity, but also can produce hydrogen bonds with the base material and the solvent, thereby increasing the solubility of the polybenzimidazole resin and increasing its acid loading level. The benzene ring has a steric hindrance effect, which can change the stacking mode and arrangement structure of the polybenzimidazole resin molecules, reduce the interaction force between the molecules, and further improve the The acid loading level of the polybenzimidazole resin is increased. The introduction of the flexible long-chain alkane structure and the ether bond not only changes the interaction force between the polybenzimidazole resin molecules, making it easier to interact with the polyphosphoric acid molecules and increasing the acid loading level of the polybenzimidazole resin molecules, but also promotes the segment movement of the polybenzimidazole resin, reduces the glass transition temperature, and improves the processability of the polybenzimidazole resin. The introduction of the trifluoromethyl group can reduce the hydrophobicity of the polybenzimidazole resin molecules and further increase its acid loading level. Through the synergistic effect of each group, the acid loading level of the polybenzimidazole resin is increased, and its processability is improved. DETAILED DESCRIPTION

[0012] In order to make the implementation methods of the present application easier to understand, the present application will be described in detail below in conjunction with specific examples. These examples are only for illustration and are not limited to the scope of application of the present application.

[0013] The present application is further described in detail below with reference to examples and comparative examples.

[0014] Preparation Examples 1-3 and Comparative Preparation Examples 1-2 provide methods for preparing functionalized dicarboxylic acids.

[0015] Preparation Example 1 This preparation example provides a method for preparing a functionalized dicarboxylic acid, wherein the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, control the ultrasonic frequency to 30kHz, the ultrasonic power to 500w, the ultrasonic treatment to 0.50h, control the rotation speed to 500rpm, stir while heating to 55°C, then add triethylamine and toluene, dropwise add epichlorohydrin, control the dripping to be completed within 10min, maintain the rotation speed unchanged, stir and react for 3h, filter after the reaction, control the rotary evaporation temperature to 82°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water three times in sequence, and dry at 55°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23:550:2.6:10:18:16; Step A2, adding epoxy monomer to anhydrous DMF, heating to 52°C, stirring at a speed of 600 rpm for 24 minutes until uniform, adding a mixed solution a of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74°C, stirring and reacting for 6 hours, adjusting the pH to neutral with 0.4M hydrochloric acid, controlling the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 3 times in sequence, and drying at 62°C to constant weight to obtain an esterified monomer, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 3:65:16, and the mass ratio of sebacic acid, tributylamine and isopropanol in the mixed solution a is 3.6:0.06:12; Step A3, add the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 450 rpm for 32 minutes until uniform, heat to reflux under nitrogen protection, maintain the speed unchanged, continue stirring to react for 6 hours, filter after the reaction, control the rotary evaporation temperature to 82°C, and rotary evaporation to remove anhydrous DMF, the rotary evaporation product is placed in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, and rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water for 3 times in sequence, and dry at 55°C to constant weight to obtain functionalized dicarboxylic acid, wherein the mass ratio of the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5:2.5:0.12:8:80:36.

[0016] Preparation Example 2 This preparation example provides a method for preparing a functionalized dicarboxylic acid, wherein the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, control the ultrasonic frequency to 35kHz, the ultrasonic power to 550w, the ultrasonic time to 0.55h, control the rotation speed to 550rpm, raise the temperature to 60°C while stirring, then add triethylamine and toluene, drop epichlorohydrin, control the dripping to be completed within 10min, after the dripping is completed, stir and react for 3.5h, filter after the reaction, control the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 40°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water 4 times in sequence, and dry at 60°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 29:595:3.0:12:21:18; Step A2, adding epoxy monomer to anhydrous DMF, heating to 54°C, stirring at a speed of 650rpm for 26min until uniform, adding a mixed solution a of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30min. After the dripping is completed, heating to 76°C, stirring and reacting for 8h, adjusting the pH to neutral with 0.6M hydrochloric acid, controlling the rotary evaporation temperature to 86°C, rotary evaporating to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 4 times in sequence, and drying at 64°C to constant weight, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 4:70:16, and the mass ratio of sebacic acid, tributylamine and isopropanol in the mixed solution a is 4.8:0.08:13; Step A3, add esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 500 rpm for 34 minutes until uniform, heat to reflux under nitrogen protection, maintain the speed unchanged, continue stirring to react for 7 hours, after the reaction is completed, control the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, the rotary evaporation product is dissolved in acetone, filtered, control the rotary evaporation temperature to 40°C, rotary evaporation to remove acetone, and then wash with anhydrous ethanol and deionized water for 4 times in sequence, and dry at 60°C to constant weight to obtain functionalized dicarboxylic acid, wherein the mass ratio of esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 6:3.0:0.14:10:85:39.

[0017] Preparation Example 3 This preparation example provides a method for preparing a functionalized dicarboxylic acid, wherein the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, control the ultrasonic frequency to 40kHz, the ultrasonic power to 600w, the ultrasonic for 0.6h, control the rotation speed to 600rpm, stir and heat to 65°C, then add triethylamine and toluene, drop epichlorohydrin, control the dripping to be completed within 10min, stir and react for 4h after the dripping, filter after the reaction, control the rotary evaporation temperature to 86°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 42°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water for 5 times in sequence, and dry at 65°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 35:640:3.4:14:24:20; Step A2, adding epoxy monomer to anhydrous DMF, heating to 56°C, stirring at a speed of 700 rpm for 28 minutes until uniform, adding a mixed solution a of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 80°C, maintaining the speed unchanged, and continuing to stir and react for 10 hours, adjusting the pH to neutral with 0.6M hydrochloric acid, controlling the rotary evaporation temperature to 86°C, rotary evaporating to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 5 times in sequence, and drying at 66°C to constant weight, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 5:75:16, and the mass ratio of sebacic acid, tributylamine and isopropanol in the mixed solution a is 6.2:0.10:14; Step A3, add esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 550 rpm for 36 minutes until uniform, under nitrogen protection, heat to reflux, maintain the speed unchanged, continue stirring to react for 8 hours, after the reaction is completed, control the rotary evaporation temperature to 86°C, rotary evaporation to remove anhydrous DMF, the rotary evaporation product is placed in acetone to dissolve, filter, control the rotary evaporation temperature to 42°C, rotary evaporation to remove acetone, and then wash with anhydrous ethanol and deionized water for 5 times in sequence, and dry at 65°C to constant weight to obtain functionalized dicarboxylic acid, wherein the mass ratio of esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 7:3.5:0.16:12:90:42.

[0018] Comparative Preparation Example 1 This comparative preparation example provides a method for preparing a functionalized dicarboxylic acid, and the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse m-aminobenzoic acid in anhydrous DMF, control the ultrasonic frequency to 30kHz, the ultrasonic power to 500w, the ultrasonic treatment to 0.50h, control the rotation speed to 500rpm, raise the temperature to 55°C while stirring, then add triethylamine and toluene, dropwise add epichlorohydrin, control the dripping to be completed within 10min, maintain the rotation speed unchanged, stir and react for 3h, filter after the reaction, control the rotary evaporation temperature to 82°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water three times in sequence, and dry at 55°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of m-aminobenzoic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23:550:2.6:10:18:16; Step A2, adding epoxy monomer to anhydrous DMF, heating to 52°C, stirring at a speed of 600 rpm for 24 minutes until uniform, adding a mixed solution a of malonic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74°C, stirring and reacting for 6 hours, adjusting the pH to neutral with 0.4M hydrochloric acid, controlling the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 3 times in sequence, and drying at 62°C to constant weight to obtain an esterified monomer, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 3:65:16, and the mass ratio of malonic acid, tributylamine and isopropanol in the mixed solution a is 3.6:0.06:12; Step A3, add the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 450 rpm for 32 minutes until uniform, heat to reflux under nitrogen protection, maintain the speed unchanged, continue stirring to react for 6 hours, filter after the reaction, control the rotary evaporation temperature to 82°C, and rotary evaporation to remove anhydrous DMF, the rotary evaporation product is placed in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, and rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water for 3 times in sequence, and dry at 55°C to constant weight to obtain functionalized dicarboxylic acid, wherein the mass ratio of the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5:2.5:0.12:8:80:36.

[0019] Comparative Preparation Example 2 This comparative preparation example provides a method for preparing a functionalized dicarboxylic acid, and the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, control the ultrasonic frequency to 30kHz, the ultrasonic power to 500w, the ultrasonic treatment to 0.50h, control the rotation speed to 500rpm, stir while heating to 55°C, then add triethylamine and toluene, dropwise add epichlorohydrin, control the dripping to be completed within 10min, maintain the rotation speed unchanged, stir and react for 3h, filter after the reaction, control the rotary evaporation temperature to 82°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water three times in sequence, and dry at 55°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23:550:2.6:10:18:16; Step A2, adding epoxy monomer to anhydrous DMF, heating to 52°C, stirring at a speed of 600 rpm for 24 minutes until uniform, adding a mixed solution a of malonic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74°C, stirring and reacting for 6 hours, adjusting the pH to neutral with 0.4M hydrochloric acid, controlling the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 3 times in sequence, and drying at 62°C to constant weight to obtain an esterified monomer, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 3:65:16, and the mass ratio of malonic acid, tributylamine and isopropanol in the mixed solution a is 3.6:0.06:12; Step A3, add the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 450 rpm for 32 minutes until uniform, heat to reflux under nitrogen protection, maintain the speed unchanged, continue stirring to react for 6 hours, filter after the reaction, control the rotary evaporation temperature to 82°C, and rotary evaporation to remove the anhydrous DMF, the rotary evaporation product is placed in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, and rotary evaporation to remove the acetone, then wash with anhydrous ethanol and deionized water for 3 times in sequence, and dry at 55°C to constant weight to obtain a functionalized dicarboxylic acid, wherein the mass ratio of the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5:2.5:0.12:8:80:22.

[0020] Comparative Preparation Example 3 This comparative preparation example provides a method for preparing a functionalized dicarboxylic acid, and the functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, control the ultrasonic frequency to 30kHz, the ultrasonic power to 500w, the ultrasonic treatment to 0.50h, control the rotation speed to 500rpm, stir while heating to 55°C, then add triethylamine and toluene, dropwise add epichlorohydrin, control the dripping to be completed within 10min, maintain the rotation speed unchanged, stir and react for 3h, filter after the reaction, control the rotary evaporation temperature to 82°C, rotary evaporation to remove anhydrous DMF, place the rotary evaporation product in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water three times in sequence, and dry at 55°C to constant weight to obtain an epoxy monomer, wherein the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23:550:2.6:10:18:16; Step A2, adding epoxy monomer to anhydrous DMF, heating to 52°C, stirring at a speed of 600 rpm for 24 minutes until uniform, adding a mixed solution a of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74°C, stirring and reacting for 6 hours, adjusting the pH to neutral with 0.4M hydrochloric acid, controlling the rotary evaporation temperature to 84°C, rotary evaporation to remove anhydrous DMF, and then washing with anhydrous ethanol and deionized water for 3 times in sequence, and drying at 62°C to constant weight to obtain an esterified monomer, wherein the mass ratio of epoxy monomer, anhydrous DMF and mixed solution a is 3:65:16, and the mass ratio of sebacic acid, tributylamine and isopropanol in the mixed solution a is 3.6:0.06:12; Step A3, add the esterification monomer, 1-(2-chloroethyl)-3-methylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir at a speed of 450 rpm for 32 minutes until uniform, heat to reflux under nitrogen protection, maintain the speed unchanged, continue stirring to react for 6 hours, filter after the reaction, control the rotary evaporation temperature to 82°C, and rotary evaporation to remove anhydrous DMF, the rotary evaporation product is placed in acetone to dissolve, filter, control the rotary evaporation temperature to 36°C, and rotary evaporation to remove acetone, then wash with anhydrous ethanol and deionized water for 3 times in sequence, and dry at 55°C to constant weight to obtain a functionalized dicarboxylic acid, wherein the mass ratio of the esterification monomer, 1-(2-chloroethyl)-3-methylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5:2.5:0.12:8:80:36.

[0021] Examples 1-3 and Comparative Examples 1-3 provide a method for synthesizing a polybenzimidazole resin.

[0022] Example 1 This embodiment provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 3 parts of 3,3'-diaminobenzidine, 7.8 parts of the functionalized dicarboxylic acid prepared in Preparation Example 1, 500 parts of polyphosphoric acid, 28 parts of deionized water and 220 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 10%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 20 min at a controlled speed of 500 rpm until uniform, heating to 195°C at a gradient rate of 39°C / h under nitrogen protection, maintaining the speed unchanged, and continuing stirring to react for 18 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 3 times, and drying at 55°C to constant weight to obtain polybenzimidazole resin.

[0023] Example 2 This embodiment provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 4 parts of 3,3'-diaminobenzidine, 10.35 parts of the functionalized dicarboxylic acid prepared in Preparation Example 2, 600 parts of polyphosphoric acid, 30 parts of deionized water and 230 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 15%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 25 min at a controlled speed of 600 rpm until uniform, heating to 205°C at a gradient rate of 41°C / h under nitrogen protection, maintaining the speed unchanged, and continuing stirring to react for 20 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 4 times, and drying at 60°C to constant weight to obtain polybenzimidazole resin.

[0024] Example 3 This embodiment provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 5 parts of 3,3'-diaminobenzidine, 12.9 parts of the functionalized dicarboxylic acid prepared in Preparation Example 3, 700 parts of polyphosphoric acid, 32 parts of deionized water and 240 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 20%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 30 min at a controlled speed of 700 rpm until uniform, heating to 215°C at a gradient rate of 43°C / h under nitrogen protection, and continuing stirring to react for 22 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 5 times, and drying at 65°C to constant weight to obtain polybenzimidazole resin.

[0025] Comparative Example 1 This comparative example provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 3 parts of 3,3'-diaminobenzidine, 7.8 parts of the functionalized dicarboxylic acid prepared in Comparative Preparation Example 1, 500 parts of polyphosphoric acid, 28 parts of deionized water and 220 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 10%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 20 min at a controlled speed of 500 rpm until uniform, heating to 195°C at a gradient rate of 39°C / h under nitrogen protection, maintaining the speed unchanged, and continuing stirring to react for 18 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 3 times, and drying at 55°C to constant weight to obtain polybenzimidazole resin.

[0026] Comparative Example 2 This comparative example provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 3 parts of 3,3'-diaminobenzidine, 7.8 parts of the functionalized dicarboxylic acid prepared in Comparative Preparation Example 2, 500 parts of polyphosphoric acid, 28 parts of deionized water and 220 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 10%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 20 min at a controlled speed of 500 rpm until uniform, heating to 195°C at a gradient rate of 39°C / h under nitrogen protection, maintaining the speed unchanged, and continuing stirring to react for 18 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 3 times, and drying at 55°C to constant weight to obtain polybenzimidazole resin.

[0027] Comparative Example 3 This comparative example provides a method for synthesizing a polybenzimidazole resin, which comprises the following steps: Step S1, preparing the following raw materials in parts by weight: 3 parts of 3,3'-diaminobenzidine, 7.8 parts of the functionalized dicarboxylic acid prepared in Comparative Preparation Example 3, 500 parts of polyphosphoric acid, 28 parts of deionized water and 220 parts of a pH adjuster, wherein the pH adjuster is an ammonia solution with a mass fraction of 10%; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring for 20 min at a controlled speed of 500 rpm until uniform, heating to 195°C at a gradient rate of 39°C / h under nitrogen protection, maintaining the speed unchanged, and continuing stirring to react for 18 h. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing with deionized water 3 times, and drying at 55°C to constant weight to obtain polybenzimidazole resin.

[0028] Performance Testing The polybenzimidazole resin prepared in Examples 1-3 and Comparative Examples 1-3 was cut into strips of film samples with a specification of 2 cm × 3 cm, and the length, width, thickness and mass were recorded. At a water bath temperature of 80°C, it was immersed in a phosphoric acid solution with a concentration of 85% for 48 hours, and the phosphoric acid on its surface was wiped off with filter paper, and the length, width, thickness and mass of the film after immersion were recorded. The formula for calculating the phosphoric acid doping rate of the film is as follows:

[0029] ADL is the phosphoric acid doping rate, Wd and Wo are the mass of the PBI membrane before and after immersion, respectively; MPA and MPBI are the molecular weights of phosphoric acid and PBI repeating units, respectively. The specific test results are shown in Table 1; The polybenzimidazole resins prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to DMA test to measure their glass transition temperatures Tg. The instrument model was DMAQ800 (TA Instruments, USA). The specific test results are shown in Table 1.

[0030] Table 1 Performance test of polybenzimidazole resin synthesized in Examples 1-3 and Comparative Examples 1-3

[0031] It can be seen from Table 1 that, compared with Comparative Examples 1-3, the polybenzimidazole resin synthesized in Examples 1-3 has a higher phosphoric acid doping rate and a lower glass transition temperature.

[0032] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A method for synthesizing a polybenzimidazole resin, characterized in that: The following steps are involved: Step S1, preparing the following raw materials in parts by weight: 3-5 parts of 3,3'-diaminobenzidine, 7.8-12.9 parts of functionalized dicarboxylic acid, 500-700 parts of polyphosphoric acid, 28-32 parts of deionized water and 220-240 parts of pH regulator; Step S2, synthesizing polybenzimidazole resin: adding 3,3'-diaminobenzidine and functionalized dicarboxylic acid to polyphosphoric acid, stirring evenly, and gradually heating to 195-215°C under nitrogen protection, and continuing stirring to react for 18-22 hours. After the reaction is completed, adding deionized water, filtering, adding a pH adjuster, filtering, washing, and drying to obtain polybenzimidazole resin; The functionalized dicarboxylic acid is first subjected to a nucleophilic substitution reaction with 6-aminopyridine-2-carboxylic acid and epichlorohydrin to obtain an epoxy monomer, which is then subjected to a ring-opening esterification reaction with sebacic acid to obtain an esterified monomer, and finally subjected to a nucleophilic substitution reaction with 1-chloromethyl-3-trifluoromethylbenzene to obtain the functionalized dicarboxylic acid.

2. The method for preparing a polybenzimidazole resin according to claim 1, wherein: The functionalized dicarboxylic acid is prepared by the following steps: Step A1, ultrasonically disperse 6-aminopyridine-2-carboxylic acid in anhydrous DMF, raise the temperature to 55-65° C. while stirring, then add triethylamine and toluene, add epichlorohydrin dropwise, and control the dripping to be completed within 10 minutes. After the dripping is completed, stir and react for 3-4 hours. After the reaction is completed, filter, rotary evaporate, dissolve the rotary evaporated product in acetone, filter, rotary evaporate the filtrate, wash and dry to obtain an epoxy monomer; Step A2, adding epoxy monomer to anhydrous DMF, heating to 52-56°C, stirring evenly, adding a mixture of sebacic acid, tributylamine and isopropanol dropwise while stirring, and controlling the dripping to be completed within 30 minutes. After the dripping is completed, heating to 74-80°C, stirring and reacting for 6-10 hours, adjusting the pH to neutral, rotary evaporating, washing and drying to obtain an esterified monomer; Step A3, add the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine and anhydrous toluene to anhydrous DMF, stir evenly, heat to reflux under nitrogen protection, stir and react for 6-8 hours. After the reaction is completed, filter and rotary evaporate, dissolve the rotary evaporated product in acetone, filter, rotary evaporate the filtrate, wash and dry to obtain a functionalized dicarboxylic acid.

3. The method for preparing a polybenzimidazole resin according to claim 2, wherein: In the step A1, the mass ratio of 6-aminopyridine-2-carboxylic acid, anhydrous DMF, triethylamine, toluene, epichlorohydrin and acetone is 23-35:550-640:2.6-3.4:10-14:18-24:16-20.

4. The method for preparing a polybenzimidazole resin according to claim 2, wherein: In the step A2, the mass ratio of the epoxy monomer, anhydrous DMF and the mixed solution a is 3-5:65-75:

16.

5. The method for preparing a polybenzimidazole resin according to claim 2, wherein: In the mixed solution a, the mass ratio of sebacic acid, tributylamine and isopropanol is 3.6-6.2:0.06-0.10:12-14.

6. The method for preparing a polybenzimidazole resin according to claim 1, characterized in that: In the step A3, the mass ratio of the esterification monomer, 1-chloromethyl-3-trifluoromethylbenzene, triethylamine, anhydrous toluene, anhydrous DMF and acetone is 5-7: 2.5-3.5: 0.12-0.16: 8-12: 80-90: 36-42.

7. The method for synthesizing a polybenzimidazole resin according to claim 1, characterized in that: In step S2, the biological rate of the gradient temperature increase is 39-43°C / h.

8. The method for synthesizing a polybenzimidazole resin according to claim 1, characterized in that: The pH regulator is an ammonia solution with a mass fraction of 10-20%.

Images