The Refined Preparation And Polymerization Research Of 4,6-Diamino-1,3-Benzenediol Dihydrochloride

Poly-p-phenylenebenzobisthiazole fiber was regarded as the 21 th “super fiber” due to its its good mechanical properties, outstanding fire resistance and thermal resistance,which attracted much attention, so that PBO fiber presents broad application prospects in military, aeroapace and firefighting fields. As a monomer of this polymer, the refined preparation and polymerization research of 4,6-Diamino-1,3-benzenediol dihydrochloride(DAR?2HCl)has a very important practical significance.An intensive study on the synthesis process of DAR?2HCl has be done in this paper. Using 2,6-dihydroxybenzoic acid as material, we got the target molecule DAR?2HCl through nitration, decarboxylation,reduction. The influence factors of reactions were discussed and the optimal technological condition was determined. The purity analysis of product was done with HPLC and the structure and composition was characterized by FT-IR, 13C-NMR, 1H-NMR and the elemental analysis.This paper proposes the purification technology of DAR?2HCl, which was purified with hydrochloric acid as solvent by recrystallization. The influence factors of monomer recrystallization including chlorohydric acid concentration, dosage of chlorohydric acid,activated carbon and stannous chloride were explored, and the best purification conditions were determined. Through recrystallization, the purity of DAR?2HCl can up to 99.9% with a yield of 78.3%.DAR?2HCl was applied to the synthesis of PBO fiber.Polyphosphoric acid(PPA)was used as reaction solvent and catalyst, PBO polymer was prepared through the method of aqueous solution polymerization, and the optimum polymerization process was determined by exploring the influence of P2O5 concentration, polymer content,temperature program. The the structure of PBO polymer was characterized by FT-IR.The inherent viscosity of the polymer using dimethyl terephthalic acid method and terephthalic acid method was respectively 11.75 dL/g and 20.12 dL/g by Ubbelohde viscometer and the viscosity-average molar mass was 17280g/mol and 23297g/mol. The thermodynamic performance of it was characterized by TG.