Study On The Purification Methods Of 4,6-diamino-resorcinol Hydrochloride

Poly(p-phenylene-256-benzobisoxazoles)PBO fiber has high strength,low density,high modulus,good flame retardant and high heat resistance,etc.It is widely used in special fields such as aerospace,national defense,traffic bridge,bulletproof and fireproof clothing and competitive sports.4,6-diamino-resorcinol hydrochloride is one of the important monomers for the synthesis of PBO polymer.At present,the purification of 4,6-diamino-resorcinol hydrochloride is mostly carried out by the method of multiple cooling crystallization.This method has many problems,such as complicated process,high requirement of experimental conditions,easy adhesion and agglomeration of precipitated crystals.In order to solve this problem,in this paper,antisolvent crystallization and interfacial crystallization were used to purify 4.6-diamino-resorcinol hydrochloride for the first time under the optimal technological conditions of cooling crystallization method.To compare,the traditional cooling crystallization method was used to purify 4.6-diaminoresorcinol hydrochloride.Ethanol was selected as the solvent to determine the best cooling crystallization process conditions.The purity of the product was greater than 99.9%and the maximum yield was 45.8%.The product was characterized by high performance liquid phase,infrared spectrum and nuclear magnetic resonance hydrogen spectrum.It was proved that the product was 4.6-diamino-resorcinol hydrochloride.The crystallinity of the product was obtained by X-ray powder diffraction(XRD)analysis.The interfacial crystallization method was used to purify 4,6-diamino-resorcinol hydrochloride monomer.Water was selected as solvent and ethyl acetate was added to the monomer.The optimum process parameters of interfacial crystallization method were studied.The purity of the product was more than 99.9%and the yield was 58.2%.By HPLC?FTIR and 1H-NMR,the product was proved to be 4,6-diamino-resorcinol hydrochloride.XRD analysis showed that the crystal molecules were arranged orderly and the crystallinity was high.Antisolvent crystallization method was the best crystallization method by comparing it with interfacial crystallization and traditional cooling crystallization method.The purification of 4,6-diamino-resorcinol hydrochloride monomer was studied by antisolvent crystallization method.ethanol as the main solvent and ethyl acetate as the antisolvent agent were selected to explore the optimum process parameters of antisolvent crystallization method.the product purity was more than 99.9%and the yield was 90.1%under the optimal process conditions.The products were characterized by high performance liquid chromatography(HPLC),infrared spectroscopy(FTIR)and nuclear magnetic resonance(1HNMR).XRD analysis showed that the crystal molecules were arranged in order and the degree of crystallization was high.