Study on the synthetic technology of 4,6-Diaminoresorcinol dichloride

4,6-Diaminoresorcinol dichloride (DADHB) is one of the monomers for the production of poly (p-phenylene benzobisoxazole) (PBO), which has an excellent combination property, such as high tensile strength, high stiffness, high thermal stability and others. Beginning from the raw material - 1,2,3-trichlorobenzene, the traditional route of DADHB production consists of three reaction steps - nitration, hydrolization and catalytic hydrogenation and this traditional route suffers some defects, such as it is hard to control the operation during the hydrolytic stage and the final product DADHB is easily contaminated by NaCl formed in the hydrogenation stage. Pointing to these defects, some improvements were proposed. For the hydrolytic stage, the suitable adding mole ratio of NaOH to l,2,3-chloro-4,6-dinitobanzeno is taken as 4:1 and filtrate the hydrolysate directly other than using ethyl acetate as extractant; for the hydrogenation stage, instate of in HAc/NaAc buffer solution, the 2-chloro-4,6-dinitro-resorcinol is hydrogenated in HAc aqueous solution and no NaAc is added. Meanwhile the final product DADHB and the intermediate products of each step were analysed by FT-IR, elemental analysis, ¹HNMR ¹³C NMR and others, respectively. The results show that the modified process proposed overcomes the defects of the traditional route well.