Research Of Synthesization And Technology Of Monomer Prepared PIPD Fiber

Poly{2,6-dimidazo[4,5-b:4',5'-e]pyridinylene-1,4(2,5-dihydroxy)Phenylene} (PIPD) fiber both belongs to high performance benzoxzzole fiber. Compared to PBO fiber, PIPD fiber possesses better interfacial adhesion property and compressive property because of strong intermolecular and intramolecular hydrogen bonds between the molecules and adjacent chains, so PIPD fiber has a more wide development prospects. In this research, our work focus on synthesis and process optimization of 2, 3, 5, 6-tetraaminopyridine (TAP) and 2,5-Dihydroxyterephthalic acid (DHTA) monomers of PIPD fiber.2, 6-diamino-3,5-dinitropyridine (DADNP) was prepared by nitation of 2, 6-diaminopyridine (DAP) in an two-step mixed acid (oleum and fuming nitric acid) process, and the influencing factors of nitration reaction were discussed. The chemical structures of DADNP were characterized by FT-IR,1^H-NMR,(13)^C-NMR and elemental analysis. HPLC results shown that purity and yield of DADNP was up to above 98%, 80% respectively after the first purification.2,3,5,6-tetraaminopyridine hydrochloride salt (TAP·3HCl·H₂O) was synthesized by heterogeneous phase hydrogenation reduction of DADNP under catalytication of Pd/C in ethanol medium. The chemical structures of TAP·3HCl·H₂O were characterized by FT-IR,1^H-NMR,(13)^C-NMR and elemental analysis. The HPLC results shown that purity and yield of TAP·3HCl·H₂O was up to above 99%, 73% respectively after the first purification.2,5-dihydroxy terephthalic acid was synthesized by aromatization,basic hydrolysis of dimethyl 1,4-cyclohexanedione-2,5-dicarboxylate use I2/KI as a catalyst under H₂O2 medium, and the influencing factors of aromatization and basic hydrolysis reaction were discussed. This mrthod has advantages of simple process and high raw material utilization ratio. The chemical structures of DHTA were characterized by FT-IR,1^H-NMR,(13)^C-NMR and elemental analysis. The HPLC results shown that purity and yield of DHTA was up to above 99%, 85% respectively after the first purification.